Add global C flags to compile_commands

This solves linter warnings in editor by adding flags to ignore errors
we don't care about. This also means that compile_commands.json is
closer to the flags we actually use for compilation.

Test: Checked generated compile_commands for new flags.

Merged-In: Id583da6eb5151a9baa9a47771f5f937c88bc43f7

Change-Id: Id583da6eb5151a9baa9a47771f5f937c88bc43f7