runtime/race package contains the data race detector runtime library.
It is based on ThreadSanitizer race detector, that is currently a part of
the LLVM project.

To update the .syso files you need to:
$ svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk
$ cd compiler-rt/lib/tsan/go
$ ./buildgo.sh

Tested with gcc 4.6.1 and 4.7.0.  On Windows it's built with 64-bit MinGW.

Current runtime is built on rev 215000.