[tsan] Export __cxa_guard_ interceptors from TSan runtime. (#171921)

These functions from C++ ABI are defined in
compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp and are supposed to
replace implementations from libstdc++/libc++abi.

We need to export them similar to why we need to export other
interceptors and TSan runtime functions - e.g. if a dlopen-ed shared
library depends on `__cxa_guard_acquire`, it needs to pick up the
exported definition from the TSan runtime that was linked into the main
executable calling the dlopen()

However, because the `__cxa_guard_` functions don't use traditional
interceptor machinery, they are omitted from the auto-generated
`libclang_rt.tsan.a.syms` files. Fix this by adding them to
tsan.syms.extra file explicitly.

Co-authored-by: Vitaly Buka <vitalybuka@google.com>

Author: vonosmas

compiler-rt/lib/tsan/rtl/tsan.syms.extra

@@ -1,3 +1,6 @@
+__cxa_guard_acquire
+__cxa_guard_abort
+__cxa_guard_release
 __tsan_init
 __tsan_flush_memory
 __tsan_read*