Testing: Target uses local autoconf

This patch removes two lines where the target build (used for regression
testing) were using the active branch's configure.ac, which caused path
mismatches.  We now use our local autoconf configuration files.

This patch also fixes a typo in the source code dependencies of the
target repository.

The AC_CHECK_FILE for the solo driver has also beed removed, for the
same reason as the MOM_memory.h check.

Some comments were also added or reformatted to undocumented flags.

.testing/Makefile

@@ -32,7 +32,6 @@
 #   MPIFC   MPI Fortran compiler
 #
 # Build configuration:
-#
 #   FCFLAGS_DEBUG       Testing ("debug") compiler flags
 #   FCFLAGS_REPRO       Production ("repro") compiler flags
 #   FCFLAGS_INIT        Variable initialization flags
@@ -76,7 +75,6 @@ FCFLAGS_REPRO ?= -g -O2
 FCFLAGS_INIT ?=
 FCFLAGS_COVERAGE ?=
 # Additional notes:
-#
 # - The default values are simple, minimalist flags, supported by nearly all
 #   compilers which are comparable to GFDL's canonical DEBUG and REPRO builds.
 #
@@ -87,13 +85,14 @@ FCFLAGS_COVERAGE ?=
 #   so FCFLAGS_INIT is used to provide additional MOM6 configuration.
 
 # Set to `true` to require identical results from DEBUG and REPRO builds
+# NOTE: Many compilers (Intel, GCC on ARM64) do not yet produce identical
+#   results across DEBUG and REPRO builds (as defined below), so we disable on
+#   default.
 DO_REPRO_TESTS ?=
 
+# Time measurement (configurable by the CI)
 TIME ?= time
 
-# Many compilers (Intel, GCC on ARM64) do not yet produce identical results
-# across DEBUG and REPRO builds (as defined below), so we disable on default.
-
 #---
 # Dependencies
 DEPS = deps
@@ -158,7 +157,8 @@ MOM_SOURCE = $(call SOURCE,../src) \
   $(wildcard ../config_src/drivers/solo_driver/*.F90) \
   $(wildcard ../config_src/ext*/*/*.F90)
 TARGET_SOURCE = $(call SOURCE,build/target_codebase/src) \
-  $(wildcard build/target_codebase/config_src/solo_driver/*.F90) \
+  $(wildcard build/target_codebase/config_src/infra/FMS1/*.F90) \
+  $(wildcard build/target_codebase/config_src/drivers/solo_driver/*.F90) \
   $(wildcard build/target_codebase/config_src/ext*/*.F90)
 FMS_SOURCE = $(call SOURCE,$(DEPS)/fms/src)
 
@@ -250,7 +250,7 @@ build/target/Makefile: | $(TARGET_CODEBASE)
 #   Ideally we would want to re-run both Makefile and mkmf, but our mkmf call
 #   is inside ./configure, so we must re-run ./configure as well.
 $(foreach b,$(filter-out target,$(BUILDS)),build/$(b)/Makefile): $(MOM_SOURCE)
-build/target/configure: $(TARGET_SOURCE)
+build/target_codebase/configure: $(TARGET_SOURCE)
 
 
 # Build MOM6
@@ -287,9 +287,6 @@ $(TARGET_CODEBASE)/ac/configure: $(TARGET_CODEBASE)
 $(TARGET_CODEBASE):
 	git clone --recursive $(MOM_TARGET_URL) $@
 	cd $@ && git checkout $(MOM_TARGET_BRANCH)
-	# Copy modern autoconf files to target?
-	mkdir -p $(TARGET_CODEBASE)/ac
-	cp -r ../ac/{configure.ac,Makefile.in,m4} $(TARGET_CODEBASE)/ac
 
 
 #---

ac/configure.ac

@@ -50,7 +50,6 @@ AS_IF([test "$enable_asymmetric" = yes],
 
 # Default to solo_driver
 DRIVER_DIR=${srcdir}/config_src/drivers/solo_driver
-AC_CHECK_FILE($DRIVER_DIR, [DRIVER_DIR=$DRIVER_DIR], [DRIVER_DIR=${srcdir}/config_src/solo_driver])
 AC_ARG_WITH([driver],
   AS_HELP_STRING([--with-driver=coupled_driver|solo_driver], [Select directory for driver source code]))
 AS_IF([test "x$with_driver" != "x"],