[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 ARM-software/abi-aa#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 llvm#63418

Reviewed By: MaskRay

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

compiler-rt/lib/interception/interception.h

@@ -181,7 +181,7 @@ const interpose_substitution substitution_##func_name[]             \
 // FreeBSD's dynamic linker (incompliantly) gives non-weak symbols higher
 // priority than weak ones so weak aliases won't work for indirect calls
 // in position-independent (-fPIC / -fPIE) mode.
-#   define __ASM_WEAK_WRAPPER(func)
+#   define __ASM_WEAK_WRAPPER(func) ".globl " #func "\n"
 #  else
 #   define __ASM_WEAK_WRAPPER(func) ".weak " #func "\n"
 #  endif  // SANITIZER_FREEBSD || SANITIZER_NETBSD