gnumake: do not use MAKE_CXX

Removes unnecessary C++ compiler reference when CXX environment variable
is set to an absolute path.

pkgs/development/tools/build-managers/gnumake/default.nix

@@ -45,6 +45,17 @@ stdenv.mkDerivation rec {
     # See https://github.com/NixOS/nixpkgs/issues/51221 for discussion.
     ++ lib.optional stdenv.isDarwin "ac_cv_struct_st_mtim_nsec=no";
 
+  # Remove unnecessary reference to C++ compiler. Note that MAKE_CXX is
+  # always set to $CXX when running confugure script. If it is not set,
+  # a reasonable fallback is used.
+  #
+  # See also https://savannah.gnu.org/bugs/?63668 and make commit
+  # ffa28f3914ff402b3915f75e4fed86ac6fb1449d.
+  postPatch = ''
+    substituteInPlace configure \
+      --replace-fail 'printf "%s\n" "#define MAKE_CXX \"$CXX\"" >>confdefs.h' ""
+  '';
+
   outputs = [ "out" "man" "info" ];
   separateDebugInfo = true;