[git_cache] Allow expansion of `~` in git cache.cachepath parameter.

All git path parameters support `~` expansion, there's no reason we
shouldn't do this for cache.cachepath parameter used by gclient.

Change-Id: I92485d5f17d8ab8125074253f75e0ef2e2ff41e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5227662
Commit-Queue: Aleksey Khoroshilov <akhoroshilov@brave.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

git_cache.py

@@ -197,7 +197,8 @@ class Mirror(object):
                 try:
                     cachepath = subprocess.check_output(
                         [cls.git_exe, 'config'] + cls._GIT_CONFIG_LOCATION +
-                        ['cache.cachepath']).decode('utf-8', 'ignore').strip()
+                        ['--type', 'path', 'cache.cachepath']).decode(
+                            'utf-8', 'ignore').strip()
                 except subprocess.CalledProcessError:
                     cachepath = os.environ.get('GIT_CACHE_PATH',
                                                cls.UNSET_CACHEPATH)