Fix EROFS error when root fs is mounted read-only

repo attempts to create /etc/.repo_gitconfig.json file, and fails if
root file system is mounted read-only. Removing non-existing file on
read-only filesystem results in EROFS instead of ENOENT.

Bug: 401018409
Change-Id: I64edc0567fb88649f3fd8cacb65a8780744640d4
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/458821
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: Egor Duda <egor.duda@gmail.com>
Commit-Queue: Egor Duda <egor.duda@gmail.com>

platform_utils.py

@@ -156,6 +156,12 @@ def remove(path, missing_ok=False):
                 os.rmdir(longpath)
             else:
                 os.remove(longpath)
+        elif (
+            e.errno == errno.EROFS
+            and missing_ok
+            and not os.path.exists(longpath)
+        ):
+            pass
         elif missing_ok and e.errno == errno.ENOENT:
             pass
         else: