Some recent ARM changes turned out to break the lit tests for the MINIMAL build. Two main issues:
1. ARM tests are currently asm-only, so allow_dump needs to be required.
2. GlobalContext::emitFileHeader() needs to return gracefully instead of calling report_fatal_error(), to allow error tests to produce the right error output.
BUG= none
R=kschimpf@google.com
Review URL: https://codereview.chromium.org/1202563002
