Change sub_test to always use the compileline from CHPL_HOME

compileline can behave poorly if run from a CHPL_TEST_UTIL_DIR that is
not inside of CHPL_HOME when using a module.
Merge pull request #669 from Kyle-B/kb-subtest-compileline

Change sub_test to always use the compileline from CHPL_HOME

compileline can behave poorly if run from a CHPL_TEST_UTIL_DIR that is
not inside of CHPL_HOME when using a module.