[compiler-rt] TlsBaseAddr value for darwin arm64

getting the tls base address. unlike linux arm64, the tpidr_el0 returns always 0 (aka unused)
thus using tpidrro_el0 instead clearing up the cpu id encoded in the lower bits.

Reviewed-By: yln

Differential Revision: https://reviews.llvm.org/D112866

Author: devnexen

compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

@@ -543,6 +543,9 @@ uptr TlsBaseAddr() {
   asm("movq %%gs:0,%0" : "=r"(segbase));
 #elif defined(__i386__)
   asm("movl %%gs:0,%0" : "=r"(segbase));
+#elif defined(__aarch64__)
+  asm("mrs %x0, tpidrro_el0" : "=r"(segbase));
+  segbase &= 0x07ul;  // clearing lower bits, cpu id stored there
 #endif
   return segbase;
 }