The llvm repos commonly have access issues, so removing them will
improve stability of the Travis builds.
Filtering check_log's output through asan_symbolize also avoids the
version dance every time a new clang version makes its way into Travis.
1. CI_TARGET now determines which run_${CI_TARGET}.sh script to use. Defaults to
`tests`.
2. Build no longer halts on the first failing suit: e.g. if functional tests
failed it will continue with unit tests, etc.
3. All ${MAKE_CMD} occurrences moved to `top_make` function, added `build_make`
as an alias to `make -C build` (`"${MAKE_CMD}" -C "${BUILD_DIR}"`) which is
too verbose.
`suite.sh` was copied from powerline (tests/common.sh file), assumes running
with POSIX shells (and actually uses dash in powerline). Then some convenience
functions were added (run_test and below).
