slight change to pulling out the MENUSELECT_CFLAGS from the user and global

level makeopts files - if MENUSELECT_CFLAGS is set to nothing in the user level
makeotps file, then the Makefile should not look in the global file at all.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@36228 65c4cc65-6c06-0410-ace0-fbb531ad65f3