Add a PREUPLOAD.cfg file to run git-clang-format on every commit

The style file .clang-format is copied from adb/.clang-format.
Each sub folders still can have different style by adding their own
.clang-format because git-clang-format uses the style file located
in one of the parent directories of the *source file*.

Also see the following link for previous discussions:

  https://android-review.googlesource.com/#/c/340106

Bug: 36046320
Test: repo upload, checks pre-submit fails when the uploading commit
      doesn't meet the style

Change-Id: I94369af197da1ccce581bbd861c8737f6a197429