Revision https://reviews.llvm.org/D69384 added the option "-codegenprepare" to an invocation of
opt, which then requires LLVM to have the expected target available for
The ARM build bots do not compile this target as part of their build,
causing this test to abort:
"Trying to construct TargetPassConfig without a target machine.
Scheduling a CodeGen pass without a target triple set?"
This change skips the test as unsupported if the x86-apple target is not