Changes since release 0.4:
- Compatibility updates for bazel versions up till 2.1.1.
- Support for LLVM versions 8.0.0 and 9.0.0.
- Attribute for builtin include directories (53ce45e).
- Undefine FORTIFY_SOURCE instead of defining as 0 (9c20deb).
- Omit --gc-sections from macOS optimized builds (0cf1d78).
- Add '-undefined dynamic_lookup' to macOS linker (64bb7aa).
- Toolchain registration (if toolchain resolution is enabled through
--incompatible_enable_cc_toolchain_resolution).