The architecture doesn't really matter for the test, at least not until
the dynamic loader can load these fat64 binaries. Use Hawell instead of
arm64 to support older bots that don't know about Apple Silicon triples.
Support universal Mach-O binaries with a fat64 header. After
4d683f7fa7d4, dsymutil can now generate such binaries when the offsets
would otherwise overflow the 32-bit offsets in the regular fat header.
rdar://107289570
Differential revision: https://reviews.llvm.org/D147012