Makefile.unix: There is a sort command in the 'make savedefconfig' file. I...

Makefile.unix:  There is a sort command in the 'make savedefconfig' file.  I found that sort behaves differently on different platforms based on the environment variable LC_ALL.  Now, Makefile.unix will force LC_ALL=C just for the sort command so that we can all generate equivalent defconfig files.