Add clang_tidy_test

[keith]

This is a new test rule that executes clang-tidy as a test via shell
script instead of an aspect.

The biggest implementation issue with this is that the paths you get
from CcInfo do not match the directory structure when running clang-tidy
in a test. This requires a bit of fixing up.

This attempts to share as much logic as possible with the aspect. I
think a bit more could be shared in the future.

Based on #65

Closes: #65
Fixes: #15

[keith]

One interesting difference with the test is it runs over multiple files at once, potentially only invoking clang-tidy once per library, but it will invoke it twice if there is a C file and C++ file

[keith]

One interesting difference with the test is it runs over multiple files at once, potentially only invoking clang-tidy once per library, but it will invoke it twice if there is a C file and C++ file

im actually not sure if this is good or bad since clang-tidy seems to not run in parallel and is quite slow. but users can always make 1 test target per file if they'd prefer.

[keith]

added a data parameter so it's easy to add files without them being linted, which users can use in a macro to create 1 test target per file while still providing all the necessary files to allow clang-tidy to work

[erenon]

Thanks for the high quality contribution!

[keith]

requires ci fix: #86

[erenon]

Thanks, merged!

[keith]

thanks! sorry i should have squashed here, I assumed that would happen at merge time