Trying to invoke an x64 binary on ARM64 Windows 10 won't work, and will
print an obscure error message. Choose the 32-bit linker instead, which
will run under emulation.
The x64 linker should in theory run under ARM64 Windows 11. We could
detect this using IsWow64GuestMachineSupported(), but I don't have a
setup to test that with at the moment.
Differential Revision: https://reviews.llvm.org/D120681
This relands 73e585e44d (and 0574b5fc65), with a fix for
the failing test (by using Optional<StringRef>s instead of
making StringRef::empty() mean absence of value).
Differential Revision: https://reviews.llvm.org/D118070