Disable clang tidy checks under BitWriter*.

We don't control those files. We cannot fix warnings in them.
No point in getting tidy warnings on them.

Bug: 26936282
Test: WITH_TIDY=1 WITH_STATIC_ANALYZER=1 mm has no more warnings.
Change-Id: I694d7a0fd365c79057357071914dd1a4802fefec
3 files changed