I think sys/mount.h is only needed in the ucred.h path.
Fixes building on hurd, I think.
--- a/src/platform_unix.c Mon Apr 20 23:48:16 2009 -0400
+++ b/src/platform_unix.c Sat May 02 23:25:41 2009 -0700
@@ -23,7 +23,6 @@
#include <dirent.h>
#include <time.h>
#include <errno.h>
-#include <sys/mount.h>
#if (!defined PHYSFS_NO_PTHREADS_SUPPORT)
#include <pthread.h>
@@ -33,6 +32,7 @@
# ifdef PHYSFS_HAVE_MNTENT_H
# undef PHYSFS_HAVE_MNTENT_H /* don't do both... */
# endif
+# include <sys/mount.h>
# include <sys/ucred.h>
#endif