Adding the @skipIfAddressSanitizerUnsupported decorator, which detects whether the compiler supports "-fsanitize=address", and skips the marked tests if not. Getting rid of the stupid "findBuiltClang" logic, in favor of just using the same compiler that you use for the rest of the tests.
Related to http://reviews.llvm.org/D6205. I also updated the ASan test cases to react more properly to the "stop reason = exec", which is probably a OS X only thing, on Linux where ASan is a static library, the relaunch doesn't happen. Doug, could you try this patch on Ubuntu, if it resolves the test failure you were seeing?