fix(native-comp): compatibility with libgccjit 12 homebrew formula

Since the latest update of `libgccjit` in brew to version 12, emacs does
not build again. Problem is that now dylib exists in multiple locations,
and `MAC_CFLAGS` environment variable is not filled correctly in
`configure.ac`. This commit fixes the issue.

build-emacs-for-macos

@@ -682,6 +682,17 @@ class Build
       }
     end
 
+    if %w[emacs-28 emacs-29].include?(effective_version)
+      p << {
+        replace: [
+          'configure.ac',
+          'grep -E \'libgccjit\.(so|dylib)$\'))"',
+          'grep -E \'libgccjit\.(so|dylib)$\' | tail -1))"'
+        ],
+        allow_failure: true
+      }
+    end
+
     if effective_version == 'emacs-27'
       p << {
         url: 'https://github.com/d12frosted/homebrew-emacs-plus/raw/master/' \