LLVM sanitizers support

Just a thought that it would be nice to support llvm sanitizers (ASan and TSan at least) in miniosv.

Since we already include most of llvm libraries and libc, we would just have to define a sanitizer_miniosv.cpp in compiler-rt/lib/sanitizer_common to link the sanitizers onto our primitives. We would also have to provide a little shim to bridge the expected POSIX functions onto our methods.