cfX clang: Rework target flag layout:

cfX clang is only used on target modules, and AOSP clang is only used
on host modules in our build system. As of the AOSP's host clang overhaul,
the assumption is made that clang won't be used for the target, so
TARGET_GLOBAL_* flags are not set when clang's used (just as in the AOSP).

Until we change this, and massively cleanup ourselves, this is a little hack
to remind us that cfX clang is only used for targets, and we need these flags
to be set.