[compiler-rt] Use .globl for FreeBSD/NetBSD interceptor wrappers

On FreeBSD and NetBSD we don't use .weak due to differing semantics.
Currently we end up using no directive, which gives a local symbol,
whereas the closer thing to a weak symbol would be a global one. In
particular, both GNU and LLVM toolchains cannot handle a GOT-indirect
reference to a local symbol at a non-zero offset within a section on
AArch64 (see https://github.com/ARM-software/abi-aa/issues/217), and so
interceptors do not work on FreeBSD/arm64, failing to link with LLD.
Switching to .globl both works around this bug and more closely aligns
such non-weak platforms with weak ones.

Fixes https://github.com/llvm/llvm-project/issues/63418

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D158552