Fix incorrect use of CMAKE_CURRENT_SOURCE_DIR and CMAKE_SOURCE_DIR.
Fix incorrect use of CMAKE_CURRENT_SOURCE_DIR and CMAKE_SOURCE_DIR.

CMAKE_CURRENT_SOURCE_DIR and CMAKE_SOURCE_DIR were being used to
reference source files or cmake project files relative to the project's
directory.  Instead CMAKE_CURRENT_LIST_DIR should be used so that it's
possible to reference source files relative to the CMakeLists.txt file
in the project.

All generated files still reference CMAKE_SOURCE_DIR so they're placed
in the directory used for builds.

Tested:
Verified all targets in this project continue to build on OSX.

Bug: 25871859
Change-Id: Iee5b6718a44d011b51f5c8d9515efaaa6abfcf0a

google/breadboard,google/breadboard