Summary:
- set SHELL to bash explicitly in Makefiles (Debian uses dash)
- avoid using system headers when using our own clang's headers in tests
- do not rely on the name of the object file to write the frontend debugging scripts. It turns out that `-o` is *not* always present in the arguments of `-cc1` functions so the `Option.get` could crash. Since we don't actually need to get the object file name, just a nice enough name, don't try to be smarter at guessing what object will be created and pick a different name built from the source name instead.
Reviewed By: akotulski
Differential Revision: D4159516
fbshipit-source-id: c7bc2b9
Jules Villard