Change to user header inclusion

Build system uses '-MMD' flag which creates depfiles
containing user headers only.
Marking libunwindstack's header files as system headers results
that depfiles are missing libunwindstacks include files.
This is the root cause of failing and inconsistent incremental builds.

As an example DwarfEhFrameWithHdr.o was checked by 'ninja -t deps'
Using '-isystem' -> 4 deps
Using '-I' -> 11 deps

Change-Id: Ib9ee49899b44b4012e2e5335e8c85b5f919ad31f
Reviewed-by: Mike Wittman <>
1 file changed