[tsan] Pass correct interposed function prefix to report function

[ismailp]

Summary

On Darwin, interposed functions are prefixed with "wrap_". On Linux,
they are prefixed with "__interceptor_".

[kubamracek]

LGTM, this fixes about a dozen test failures on OS X.

[ismailp]

Thanks! Landed in r252695.

compiler-rt/trunk/lib/tsan/rtl/tsan_report.cc

 #include "tsan_platform.h"
 #include "tsan_rtl.h"
 #include "sanitizer_common/sanitizer_placement_new.h"
 #include "sanitizer_common/sanitizer_report_decorator.h"
 #include "sanitizer_common/sanitizer_stacktrace_printer.h"
 
 namespace __tsan {
 
+#if SANITIZER_MAC
+static const char *const kInterposedFunctionPrefix = "wrap_";
+#else
+static const char *const kInterposedFunctionPrefix = "__interceptor_";
+#endif
+
 ReportStack::ReportStack() : frames(nullptr), suppressable(false) {}
 
 ReportStack *ReportStack::New() {
   void *mem = internal_alloc(MBlockReportStack, sizeof(ReportStack));
   return new(mem) ReportStack();
 }
 
 ReportLocation::ReportLocation(ReportLocationType type)
if (ent == 0 || ent->frames == 0) {
     Printf("    [failed to restore the stack]\n\n");
     return;
   }
   SymbolizedStack *frame = ent->frames;
   for (int i = 0; frame && frame->info.address; frame = frame->next, i++) {
     InternalScopedString res(2 * GetPageSizeCached());
     RenderFrame(&res, common_flags()->stack_trace_format, i, frame->info,
                 common_flags()->symbolize_vs_style,
-                common_flags()->strip_path_prefix, "__interceptor_");
+                common_flags()->strip_path_prefix, kInterposedFunctionPrefix);
     Printf("%s\n", res.data());
   }
   Printf("\n");
 }
 
 static void PrintMutexSet(Vector<ReportMopMutex> const& mset) {
   for (uptr i = 0; i < mset.Size(); i++) {
     if (i == 0)