* Better handle LTO_ENABLE
Especially when calling from command line
* Replace LINK_TIME_OPTIMIZATION_ENABLE with LTO_ENABLE
* Remove long for LTO from show_options.mk
This is a place for users to put code that they might use between
keyboards. If you build the keymap mine,
/users/mine/rules.mk will be included in your build, and
/users/mine/ will be in your path - keep these things in
mind when naming your files and referencing them from other places.