ci: Streamline the old MacOS-12 CI test (AcademySoftwareFoundation#4465)

It's an old flavor not well supported by homebrew any longer, so what's
happening is that some of the dependency packages we ask to install have
to build from source, which means it takes a long long time.

By disabling OpenCV and Qt homebrew installation for it, we can make it
fast again. Neither the minimal OpenCV interop, nor osltoy (the only
thing that needs Qt) are exercised by the automated testsuite anyway, so
I don't think there's any loss of testing functionality in practice.

Signed-off-by: Larry Gritz <lg@larrygritz.com>

.github/workflows/ci.yml

@@ -512,7 +512,7 @@ jobs:
             cc_compiler: clang
             cxx_compiler: clang++
             cxx_std: 17
-            python_ver: "3.10"
+            python_ver: "3.11"
             aclang: 13
             setenvs: export INSTALL_QT=0 INSTALL_OPENCV=0
           - desc: MacOS-13

src/build-scripts/install_homebrew_deps.bash

@@ -44,7 +44,7 @@ brew install --display-times -q freetype libraw dcmtk pybind11 numpy || true
 brew install --display-times -q ffmpeg libheif ptex || true
 brew install --display-times -q tbb || true
 brew install --display-times -q openvdb || true
-if [[ "${USE_OPENCV}" != "0" ]] && [[ "${USE_OPENCV:=1}" != "0" ]] ; then
+if [[ "${USE_OPENCV}" != "0" ]] && [[ "${INSTALL_OPENCV:=1}" != "0" ]] ; then
     brew install --display-times -q opencv || true
 fi
 if [[ "${USE_QT:=1}" != "0" ]] && [[ "${INSTALL_QT:=1}" != "0" ]] ; then