Reland 3nd attempt: [lld-macho] Fix bug in reading cpuSubType field.

This reverts commit 09c5aab7.

New changes:
Temporarily skip checking the output bundle's cpu/cpu-subtype
Suspected there's a bug in selecting targets which caused the produced bundle
to be arm64 bundle (even though it was specifically linked with -arch x86_64).

The current test that link succeeded should be sufficient, because
it would have failed with "unable to find matching tagets" prior to this patch.

Differential Revision: https://reviews.llvm.org/D139572