diff --git a/pkgs/by-name/cm/cmake/setup-hook.sh b/pkgs/by-name/cm/cmake/setup-hook.sh
index 0bb0426bca824..c284e3629f796 100755
--- a/pkgs/by-name/cm/cmake/setup-hook.sh
+++ b/pkgs/by-name/cm/cmake/setup-hook.sh
@@ -9,75 +9,20 @@ fixCmakeFiles() {
     echo "fixing cmake files..."
     find "$1" -type f \( -name "*.cmake" -o -name "*.cmake.in" -o -name CMakeLists.txt \) -print |
         while read fn; do
-            sed -e 's^/usr\([ /]\|$\)^/var/empty\1^g' -e 's^/opt\([ /]\|$\)^/var/empty\1^g' < "$fn" > "$fn.tmp"
+            sed -e 's^/usr\([ /]\|$\)^/var/empty\1^g' -e 's^/opt\([ /]\|$\)^/var/empty\1^g' <"$fn" >"$fn.tmp"
             mv "$fn.tmp" "$fn"
         done
 }
 
-cmakeConfigurePhase() {
-    runHook preConfigure
-
-    # default to CMake defaults if unset
-    : ${cmakeBuildDir:=build}
-
-    export CTEST_OUTPUT_ON_FAILURE=1
-    if [ -n "${enableParallelChecking-1}" ]; then
-        export CTEST_PARALLEL_LEVEL=$NIX_BUILD_CORES
-    fi
-
-    if [ -z "${dontFixCmake-}" ]; then
-        fixCmakeFiles .
-    fi
-
-    if [ -z "${dontUseCmakeBuildDir-}" ]; then
-        mkdir -p "$cmakeBuildDir"
-        cd "$cmakeBuildDir"
-        : ${cmakeDir:=..}
-    else
-        : ${cmakeDir:=.}
-    fi
-
-    if [ -z "${dontAddPrefix-}" ]; then
-        prependToVar cmakeFlags "-DCMAKE_INSTALL_PREFIX=$prefix"
-    fi
-
-    # We should set the proper `CMAKE_SYSTEM_NAME`.
-    # http://www.cmake.org/Wiki/CMake_Cross_Compiling
-    #
-    # Unfortunately cmake seems to expect absolute paths for ar, ranlib, and
-    # strip. Otherwise they are taken to be relative to the source root of the
-    # package being built.
-    prependToVar cmakeFlags "-DCMAKE_CXX_COMPILER=$CXX"
-    prependToVar cmakeFlags "-DCMAKE_C_COMPILER=$CC"
-    prependToVar cmakeFlags "-DCMAKE_AR=$(command -v $AR)"
-    prependToVar cmakeFlags "-DCMAKE_RANLIB=$(command -v $RANLIB)"
-    prependToVar cmakeFlags "-DCMAKE_STRIP=$(command -v $STRIP)"
-
-    # on macOS we want to prefer Unix-style headers to Frameworks
-    # because we usually do not package the framework
-    prependToVar cmakeFlags "-DCMAKE_FIND_FRAMEWORK=LAST"
-
-    # we never want to use the global macOS SDK
-    prependToVar cmakeFlags "-DCMAKE_OSX_SYSROOT="
-
-    # correctly detect our clang compiler
-    prependToVar cmakeFlags "-DCMAKE_POLICY_DEFAULT_CMP0025=NEW"
-
-    # This installs shared libraries with a fully-specified install
-    # name. By default, cmake installs shared libraries with just the
-    # basename as the install name, which means that, on Darwin, they
-    # can only be found by an executable at runtime if the shared
-    # libraries are in a system path or in the same directory as the
-    # executable. This flag makes the shared library accessible from its
-    # nix/store directory.
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_NAME_DIR=${!outputLib}/lib"
+genCmakeDefaultFlags() {
+    declare -ga cmakeDefaultFlags=()
 
     # The docdir flag needs to include PROJECT_NAME as per GNU guidelines,
     # try to extract it from CMakeLists.txt.
     if [[ -z "$shareDocName" ]]; then
         local cmakeLists="${cmakeDir}/CMakeLists.txt"
         if [[ -f "$cmakeLists" ]]; then
-            local shareDocName="$(grep --only-matching --perl-regexp --ignore-case '\bproject\s*\(\s*"?\K([^[:space:]")]+)' < "$cmakeLists" | head -n1)"
+            local shareDocName="$(grep --only-matching --perl-regexp --ignore-case '\bproject\s*\(\s*"?\K([^[:space:]")]+)' <"$cmakeLists" | head -n1)"
         fi
         # The argument sometimes contains garbage or variable interpolation.
         # When that is the case, let’s fall back to the derivation name.
@@ -90,41 +35,104 @@ cmakeConfigurePhase() {
         fi
     fi
 
-    # This ensures correct paths with multiple output derivations
-    # It requires the project to use variables from GNUInstallDirs module
-    # https://cmake.org/cmake/help/latest/module/GNUInstallDirs.html
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_BINDIR=${!outputBin}/bin"
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_SBINDIR=${!outputBin}/sbin"
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_INCLUDEDIR=${!outputInclude}/include"
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_OLDINCLUDEDIR=${!outputInclude}/include"
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_MANDIR=${!outputMan}/share/man"
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_INFODIR=${!outputInfo}/share/info"
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_DOCDIR=${!outputDoc}/share/doc/${shareDocName}"
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_LIBDIR=${!outputLib}/lib"
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_LIBEXECDIR=${!outputLib}/libexec"
-    prependToVar cmakeFlags "-DCMAKE_INSTALL_LOCALEDIR=${!outputLib}/share/locale"
+    cmakeDefaultFlags+=(
+        # We should set the proper `CMAKE_SYSTEM_NAME`.
+        # http://www.cmake.org/Wiki/CMake_Cross_Compiling
+        #
+        # Unfortunately cmake seems to expect absolute paths for ar, ranlib, and
+        # strip. Otherwise they are taken to be relative to the source root of the
+        # package being built.
+        "-DCMAKE_CXX_COMPILER=$CXX"
+        "-DCMAKE_C_COMPILER=$CC"
+        "-DCMAKE_AR=$(command -v $AR)"
+        "-DCMAKE_RANLIB=$(command -v $RANLIB)"
+        "-DCMAKE_STRIP=$(command -v $STRIP)"
+
+        # on macOS we want to prefer Unix-style headers to Frameworks
+        # because we usually do not package the framework
+        "-DCMAKE_FIND_FRAMEWORK=LAST"
+
+        # we never want to use the global macOS SDK
+        "-DCMAKE_OSX_SYSROOT="
+
+        # correctly detect our clang compiler
+        "-DCMAKE_POLICY_DEFAULT_CMP0025=NEW"
+
+        # This installs shared libraries with a fully-specified install
+        # name. By default, cmake installs shared libraries with just the
+        # basename as the install name, which means that, on Darwin, they
+        # can only be found by an executable at runtime if the shared
+        # libraries are in a system path or in the same directory as the
+        # executable. This flag makes the shared library accessible from its
+        # nix/store directory.
+        "-DCMAKE_INSTALL_NAME_DIR=${!outputLib}/lib"
+
+        # This ensures correct paths with multiple output derivations
+        # It requires the project to use variables from GNUInstallDirs module
+        # https://cmake.org/cmake/help/latest/module/GNUInstallDirs.html
+        "-DCMAKE_INSTALL_BINDIR=${!outputBin}/bin"
+        "-DCMAKE_INSTALL_SBINDIR=${!outputBin}/sbin"
+        "-DCMAKE_INSTALL_INCLUDEDIR=${!outputInclude}/include"
+        "-DCMAKE_INSTALL_OLDINCLUDEDIR=${!outputInclude}/include"
+        "-DCMAKE_INSTALL_MANDIR=${!outputMan}/share/man"
+        "-DCMAKE_INSTALL_INFODIR=${!outputInfo}/share/info"
+        "-DCMAKE_INSTALL_DOCDIR=${!outputDoc}/share/doc/${shareDocName}"
+        "-DCMAKE_INSTALL_LIBDIR=${!outputLib}/lib"
+        "-DCMAKE_INSTALL_LIBEXECDIR=${!outputLib}/libexec"
+        "-DCMAKE_INSTALL_LOCALEDIR=${!outputLib}/share/locale"
+
+        # Always build Release, to ensure optimisation flags
+        "-DCMAKE_BUILD_TYPE=${cmakeBuildType:-Release}"
+
+        # Disable user package registry to avoid potential side effects
+        # and unecessary attempts to access non-existent home folder
+        # https://cmake.org/cmake/help/latest/manual/cmake-packages.7.html#disabling-the-package-registry
+        "-DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON"
+        "-DCMAKE_FIND_USE_PACKAGE_REGISTRY=OFF"
+        "-DCMAKE_FIND_USE_SYSTEM_PACKAGE_REGISTRY=OFF"
+    )
+
+    if [ -z "${dontAddPrefix-}" ]; then
+        cmakeDefaultFlags+=("-DCMAKE_INSTALL_PREFIX=$prefix")
+    fi
 
     # Don’t build tests when doCheck = false
     if [ -z "${doCheck-}" ]; then
-        prependToVar cmakeFlags "-DBUILD_TESTING=OFF"
+        cmakeDefaultFlags+=("-DBUILD_TESTING=OFF")
     fi
 
-    # Always build Release, to ensure optimisation flags
-    prependToVar cmakeFlags "-DCMAKE_BUILD_TYPE=${cmakeBuildType:-Release}"
+    if [ "${buildPhase-}" = ninjaBuildPhase ]; then
+        cmakeDefaultFlags+=("-GNinja")
+    fi
+}
+
+cmakeConfigurePhase() {
+    runHook preConfigure
 
-    # Disable user package registry to avoid potential side effects
-    # and unecessary attempts to access non-existent home folder
-    # https://cmake.org/cmake/help/latest/manual/cmake-packages.7.html#disabling-the-package-registry
-    prependToVar cmakeFlags "-DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON"
-    prependToVar cmakeFlags "-DCMAKE_FIND_USE_PACKAGE_REGISTRY=OFF"
-    prependToVar cmakeFlags "-DCMAKE_FIND_USE_SYSTEM_PACKAGE_REGISTRY=OFF"
+    # default to CMake defaults if unset
+    : ${cmakeBuildDir:=build}
 
-    if [ "${buildPhase-}" = ninjaBuildPhase ]; then
-        prependToVar cmakeFlags "-GNinja"
+    export CTEST_OUTPUT_ON_FAILURE=1
+    if [ -n "${enableParallelChecking-1}" ]; then
+        export CTEST_PARALLEL_LEVEL=$NIX_BUILD_CORES
     fi
 
+    if [ -z "${dontFixCmake-}" ]; then
+        fixCmakeFiles .
+    fi
+
+    if [ -z "${dontUseCmakeBuildDir-}" ]; then
+        mkdir -p "$cmakeBuildDir"
+        cd "$cmakeBuildDir"
+        : ${cmakeDir:=..}
+    else
+        : ${cmakeDir:=.}
+    fi
+
+    genCmakeDefaultFlags
+
     local flagsArray=()
-    concatTo flagsArray cmakeFlags cmakeFlagsArray
+    concatTo flagsArray cmakeDefaultFlags cmakeFlags cmakeFlagsArray
 
     echoCmd 'cmake flags' "${flagsArray[@]}"