threaded-grep cause msys build failure

Hi,

Building git in msys environment fails:
...
    LINK git.exe
builtin-grep.o: In function `wait_all':
D:\devel\msysgit\git/builtin-grep.c:260: undefined reference to
`pthread_cond_broadcast'
collect2: ld returned 1 exit status
make: *** [git.exe] Error 1

I guess compat/win32/pthread.c misses pthread_cond_broadcast implementation.

Zé