Allow for more targetted builds
What
This MR adds some variables that can be set (if desired by the user) to trim down the YARR build.
It adds two variables: SELECT_LIBS and SELECT_TOOLS. If set, these variables are used to filter out the lists of YARR_CONTROLLERS_TO_BUILD, YARR_FRONTENDS_TO_BUILD, and the list of executables to build such that these lists only contain the items specified in SELECT_LIBS and SELECT_TOOLS.
Usage
$ cd /path/to/YARR/build
$ cmake3 -DSELECT_LIBS=rd53b;spec -DSELECT_TOOLS=scanConsole