[third_party/yasm] Add option to ignore errors.

Some asm files use defines from the asm (e.g. CONSTANT equ VALUE) in the
preprocessor %if tests. These cannot be referenced in a pass that only
preprocesses and that creates errors, but the dependencies will print
fine and invocations that also assemble will succeed.

TEST: Used in building ffmpeg and libvpx.
Change-Id: Ia5cb58b4af2580b3904d0966120f0e0b6ad095e3
2 files changed