[sanitizer_common] Fix build on ppc64+musl (#120036)
In powerpc64-unknown-linux-musl, signal.h does not include asm/ptrace.h,
which causes "member access into incomplete type 'struct pt_regs'"
errors. Include the header explicitly to fix this.
Also in sanitizer_linux_libcdep.cpp, there is a usage of TlsPreTcbSize
which is not defined in such a platform. Guard the branch with macro.
(cherry picked from commit 801b519dfd01e21da0be17aa8f8dc2ceb0eb9e77)
