Add no-op implmentation of dirfd().

Fixes build on pre-POSIX.1 2008 systems.

Author: daztucker

openbsd-compat/bsd-misc.c

@@ -158,6 +158,15 @@ utimensat(int fd, const char *path, const struct timespec times[2],
 }
 #endif
 
+#ifndef HAVE_DIRFD
+int
+dirfd(DIR *dir)
+{
+	errno = ENOSYS;
+	return -1;
+}
+#endif
+
 #ifndef HAVE_FCHOWNAT
 /*
  * A limited implementation of fchownat() that only implements the

openbsd-compat/bsd-misc.h

@@ -65,6 +65,12 @@ struct timeval {
 int utimes(const char *, struct timeval *);
 #endif /* HAVE_UTIMES */
 
+#ifndef HAVE_DIRFD
+#include <sys/types.h>
+#include <dirent.h>
+int dirfd(DIR *);
+#endif
+
 #ifndef AT_FDCWD
 # define AT_FDCWD (-2)
 #endif