[Mono-dev] mingw-w64 build broken

[Vincent Povirk]

With current master, my mingw-w64 build is failing with the following error:

../../../mono/mono/metadata/sgen-gc.c:4855:19: error:
'mono_gc_pthread_exit' undeclared (first use in this function)

It seems to be related to commit
6427caaea886e089c7b2941137af8d918e199df0. This function is not present
in the Windows build, but I don't know if it's good enough to just
ExitThread on Windows.