Use md5 on Darwin (previously, using locally compiled coreutils md5sum)

test/functions.source

@@ -426,10 +426,8 @@ copyVideoFiles ()
 # print checksum for one file
 checkSum()
 {
-    # cygwin checksum: http://esrg.sourceforge.net/utils_win_up/md5sum/
-    # macos - built/installed coreutils 8.25 http://ftp.gnu.org/gnu/coreutils/
     platform=$(uname)
-    if [ "$platform" == 'NetBSD' -o "$platform" == 'FreeBSD' ]; then
+    if [ "$platform" == 'NetBSD' -o "$platform" == 'FreeBSD' -o "$platform" == 'Darwin' ]; then
       md5 -q $1
     else
       md5sum $1 | cut -d' ' -f 1