SystemTools: Refactor test file and directory locations

The full path for files used by SystemTools tests were preconfigured
in a generated header file by CMake variables.  This begins to get
unwieldy and clutters the CMake files once more variables and files
get added.  In preperation for more file and directory tests being
added, the preconfigured variables are now just the source and binary
directories for which all tests can base themselves off of.

Change-Id: Iae9e11592a3c040ce2e9cc90dbd1ccedfc3129ea