Special handling for some recognized env. vars.

CMake does not like that you specify the compiler with the environment
variables, instead preferring that you set them as cache variables.
This layer translate between the names of the the two.

cmake/Scripts/configure

@@ -97,6 +97,15 @@ invalid_opt () {
 
 # default values
 prefix=/usr/local
+#c_compiler=" -DCMAKE_C_COMPILER=cc"
+c_compiler=
+c_opts=
+#cxx_compiler=" -DCMAKE_CXX_COMPILER=c++"
+cxx_compiler=
+cxx_opts=
+#fort_compiler=" -DCMAKE_Fortran_COMPILER=fc"
+fort_compiler=
+fort_opts=
 #buildtype=" -DCMAKE_BUILD_TYPE=Debug"
 buildtype=
 #pch_use=" -DPRECOMPILE_HEADERS:BOOL=ON"
@@ -405,15 +414,49 @@ done
 # remove all arguments processed by getopts
 shift $((OPTIND-1))
 
-# remove Autotools-specific variables. notice the usage of a quoted
-# array: each element will be returned even with spaces.
+# notice the usage of a quoted array: each element will be returned
+# even with spaces.
 for a in "${VARS[@]}"; do
-  a="${a/ACLOCAL_*=*/}"
-  [ -n "$a" ] && ENVVARS="$ENVVARS \"${a/\"/\\\"}\""
+  case "$a" in
+    ACLOCAL_*=*)
+      # remove Autotools-specific variables. 
+      ;;
+    CC=*)
+      # special processing for compiler options
+      a=${a#CC=}
+      c_compiler=" -DCMAKE_C_COMPILER=\"${a/\"/\\\"}\""
+      ;;
+    CXX=*)
+      a=${a#CXX=}
+      cxx_compiler=" -DCMAKE_CXX_COMPILER=\"${a/\"/\\\"}\""
+      ;;
+    CFLAGS=*)
+      a=${a#CFLAGS=}
+      c_opts=" -DCMAKE_C_FLAGS=\"${a/\"/\\\"}\""
+      ;;
+    CXXFLAGS=*)
+      a=${a#CXXFLAGS=}
+      cxx_opts=" -DCMAKE_CXX_FLAGS=\"${a/\"/\\\"}\""
+      ;;
+    FC=*)
+      a=${a#FC=}
+      fort_compiler=" -DCMAKE_Fortran_COMPILER=\"${a/\"/\\\"}\""
+      ;;
+    FFLAGS=*)
+      a=${a#FFLAGS=}
+      fort_opts=" -DCMAKE_Fortran_FLAGS=\"${a/\"/\\\"}\""
+      ;;
+    *)
+      ENVVARS="$ENVVARS \"${a/\"/\\\"}\""
+      ;;
+  esac
 done
 
+# only wrap in env command if any variable were actually passed
+[ -n "${ENVVARS}" ] && ENVVARS="env ${ENVVARS} "
+
 # pass everything on to CMake
-CMDLINE="env ${ENVVARS} ${CMAKE_COMMAND} \"${srcdir}\" ${use_ninja}\"-DCMAKE_INSTALL_PREFIX=$prefix\"${buildtype}${pch_use}${silent_rules}${debug_loc}${use_openmp}${use_mpi}${use_lto}${use_runpath}${use_tests}${use_samples}${use_underscoring} ${FEATURES}"
+CMDLINE="${ENVVARS}${CMAKE_COMMAND} \"${srcdir}\" ${use_ninja}\"-DCMAKE_INSTALL_PREFIX=$prefix\"${buildtype}${pch_use}${silent_rules}${debug_loc}${use_openmp}${use_mpi}${use_lto}${use_runpath}${use_tests}${use_samples}${use_underscoring}${c_compiler}${c_opts}${cxx_compiler}${cxx_opts}${fort_compiler}${fort_opts} ${FEATURES}"
 echo --- calling CMake ---
 echo ${CMDLINE}
 eval exec ${CMDLINE}