Introduce mock codepages config option for mtools am: 32c51e05eb am: ea3799d954 am: c1a99ade63

Original change: https://android-review.googlesource.com/c/platform/external/mtools/+/2307102

Change-Id: If51ee48d5a8eac9964fd945d91fa1ba62f1596d6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>