[gtkmm/gtkmm-3-24] Detect if we build from a git subtree

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 67cdfe1d21bad7be93c40739e280175fe80c5869
Author: William Roy <wroy proton me>
Date:   Fri Sep 23 13:11:17 2022 +0000

    Detect if we build from a git subtree

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index aa9242d6..897d169f 100644
--- a/meson.build
+++ b/meson.build
@@ -61,7 +61,7 @@ endif
 cmd_py = '''
 import os
 import sys
-sys.exit(os.path.isdir("@0@") or os.path.isfile("@0@"))
+sys.exit(os.path.isdir("@0@") or os.path.isfile("@0@") or os.path.dirname("@0@"))
 '''.format(project_source_root / '.git')
 is_git_build = run_command(python3, '-c', cmd_py, check: false).returncode() != 0