See: https://trac.macports.org/ticket/71165
Upstream did not accept this solution nor provided other useful comments and/or fix.
--- mesonbuild/compilers/mixins/clike.py.orig	2026-01-06 09:36:39
+++ mesonbuild/compilers/mixins/clike.py	2026-01-06 09:47:23
@@ -1209,7 +1209,8 @@
         commands = self.get_exelist(ccache=False) + ['-v', '-E', '-']
         commands += self.get_always_args()
         # Add CFLAGS/CXXFLAGS/OBJCFLAGS/OBJCXXFLAGS from the env
-        commands += self.environment.coredata.get_external_args(self.for_machine, self.language)
+        # 'std=c++<ver>','std=gnu++<ver>' are valid for C++/ObjC++ but not for 'C'
+        commands += [x for x in self.environment.coredata.get_external_args(self.for_machine, self.language) if '-std=c++' not in x and '-std=gnu++' not in x]
         mlog.debug('Finding framework path by running: ', ' '.join(commands), '\n')
         os_env = os.environ.copy()
         os_env['LC_ALL'] = 'C'
