[7.1.0] Switch macOS minimum version flag to gcc compatible version (#…

…21219)

Fixes #20698

I'm not sure how that user got into that state yet, but it doesn't hurt
for this to be gcc compatible just in case the user is intentionally
using gcc on macOS

Closes #20798.

Commit
05b1f06

PiperOrigin-RevId: 604515755
Change-Id: Ib9087fe6afbbb3514513a7d5d120fcf448e54f65

Co-authored-by: Keith Smiley <keithbsmiley@gmail.com>

tools/cpp/unix_cc_toolchain_config.bzl

@@ -1337,7 +1337,7 @@ def _impl(ctx):
         flag_sets = [
             flag_set(
                 actions = all_compile_actions + all_link_actions,
-                flag_groups = [flag_group(flags = ["-mmacos-version-min={}".format(_target_os_version(ctx))])],
+                flag_groups = [flag_group(flags = ["-mmacosx-version-min={}".format(_target_os_version(ctx))])],
             ),
         ],
     )