work around getgrouplist signature difference on osx

src/gidcache.cpp

@@ -22,6 +22,8 @@
 
 #if defined __linux__ and UGID_USE_RWLOCK == 0
 # include <sys/syscall.h>
+#elif __APPLE__
+# include <sys/param.h>
 #endif
 
 #include <cstdlib>
@@ -90,6 +92,20 @@ gid_t_cache::lower_bound(gid_t_rec   *begin,
   return begin;
 }
 
+static
+int
+_getgrouplist(const char  *user,
+              const gid_t  group,
+              gid_t       *groups,
+              int         *ngroups)
+{
+#if __APPLE__
+  return ::getgrouplist(user,group,(int*)groups,ngroups);
+#else
+  return ::getgrouplist(user,group,groups,ngroups);
+#endif
+}
+
 gid_t_rec *
 gid_t_cache::cache(const uid_t uid,
                    const gid_t gid)
@@ -107,9 +123,9 @@ gid_t_cache::cache(const uid_t uid,
   if(pwdrv != NULL && rv == 0)
     {
       rec->size = 0;
-      ::getgrouplist(pwd.pw_name,gid,NULL,&rec->size);
+      ::_getgrouplist(pwd.pw_name,gid,NULL,&rec->size);
       rec->size = std::min(MAXGIDS,rec->size);
-      rv = ::getgrouplist(pwd.pw_name,gid,rec->gids,&rec->size);
+      rv = ::_getgrouplist(pwd.pw_name,gid,rec->gids,&rec->size);
       if(rv == -1)
         {
           rec->gids[0] = gid;