The paths were wrong in the scripts used to run tests. The same problem
was in the CMake files that used CMAKE_SOURCE_DIR instead of
CMAKE_CURRENT_SOURCE_DIR.
Added missing check for BUILD_SYSTEM_TESTS in avrorouter for the
workaround to building without all dependencies present.
The test can now be run outside of the test source directory. Since the
`test_dir` global variable contains the absolute path to the test source,
all copying of configurations and execution of scripts can be done with
minimal changes.
