[compiler-rt][rtsan] Add scoped reporting lock (#107167)

Uses a static lock to ensure multiple threads reporting issues at the
same time don't have printing collisions. This isn't so important now,
but will be with continue mode in the future.

Author: cjappl

compiler-rt/lib/rtsan/rtsan_context.cpp

@@ -91,6 +91,8 @@ bool __rtsan::Context::IsBypassed() const { return bypass_depth_ > 0; }
 
 void __rtsan::PrintDiagnostics(const char *intercepted_function_name, uptr pc,
                                uptr bp) {
+  ScopedErrorReportLock l;
+
   fprintf(stderr,
           "Real-time violation: intercepted call to real-time unsafe function "
           "`%s` in real-time context! Stack trace:\n",