The default location for multilib.yaml is lib/clang-runtimes, without
any target-specific suffix. This will allow multilibs for different
architectures to share a common include directory.
To avoid breaking the arm-execute-only.c CHECK-NO-EXECUTE-ONLY-ASM
test, add a GetExecuteOnly argument to getARMTargetFeatures.
Since the presence of multilib.yaml can change the exact location of a
library, relax the baremetal.cpp test.
I can see execute-only being used in a multilib configuration as it can impact code-generation significantly yet is a requirement for a system aiming to have all code execute-only.
Rather than a specific GenExecuteOnly flag, would it be better for something like ForMultilib like ForAS and then we could move it to not give the error message when doing ForMultilib the name would also generalise to other parts.