CONFIG: report compiler path and version from top-level build

- previously just reported gcc/clang versions, but these are not
  necessarily the ones actually being used (eg, clang-9 vs clang).
  Now use the path from `wmake -show-path-cxx` to improve the accuracy,
  and also support other compiler types.

Allwmake

@@ -15,18 +15,22 @@ wmakeCheckPwd "$WM_PROJECT_DIR" 2>/dev/null || {
 . "$WM_PROJECT_DIR"/wmake/scripts/AllwmakeParseArguments
 
 #------------------------------------------------------------------------------
-# Preamble. Report compiler version
-case "$WM_COMPILER" in
-    Gcc*)    gcc --version 2>/dev/null | sed -ne '1p' ;;
-    Clang*)  clang --version 2>/dev/null | sed -ne '1p' ;;
-esac
-
 # Preamble. Report tools or at least the mpirun location
 if [ -f "$WM_PROJECT_DIR"/wmake/scripts/list_tools ]
-then  . "$WM_PROJECT_DIR"/wmake/scripts/list_tools ]
+then  . "$WM_PROJECT_DIR"/wmake/scripts/list_tools
 else
     echo "mpirun=$(command -v mpirun || true)"
 fi
+echo
+# Report compiler information
+compiler="$(wmake -show-path-cxx 2>/dev/null || true)"
+if [ -x "$compiler" ]
+then
+    echo "compiler=$compiler"
+    "$compiler" --version 2>/dev/null | sed -ne '1p'
+else
+    echo "compiler=unknown"
+fi
 
 echo
 echo "========================================"