Bump min mac version flag.

This allows std::format to be used.

Change-Id: If8a51d0358c65977f85171b996a0033f6a6a6964
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/21480
Reviewed-by: Takuto Ikuta <tikuta@google.com>
Commit-Queue: Matt Stark <msta@google.com>

build/gen.py

diff --git a/build/gen.py b/build/gen.py
index 6ad60af..ccf8cbf 100755
--- a/build/gen.py
+++ b/build/gen.py
@@ -531,7 +531,9 @@
       ])
 
     elif platform.is_darwin():
-      min_mac_version_flag = '-mmacosx-version-min=10.12'
+      # Feel free to bump this value whenever you want, as long as all non-EOL
+      # macOS versions are supported.
+      min_mac_version_flag = '-mmacosx-version-min=14'
       cflags.append(min_mac_version_flag)
       ldflags.append(min_mac_version_flag)
     elif platform.is_aix():