[LoongArch64] XFAIL the ptrace tests requiring PTRACE_SINGLESTEP
[LoongArch64] XFAIL the ptrace tests requiring PTRACE_SINGLESTEP

The ptrace usage is not currently supported, so XFAIL for clean test
results. With this applied, all tests pass on a native LoongArch build.

Signed-off-by: WANG Xuerui <3935c444e133ed5a5bcbcc923eaa0960760835c5@gentoo.org>

libunwind/libunwind,libunwind/libunwind,libunwind/libunwind