[Python-ideas] Add .cache and compile_commands.json to .gitignote

Jack DeVries writes:

What does everyone think? Can we add these two items to the .gitignore:

• `.cache`
• `compile_commands.json`

I don't see any cost to this -- .cache is uncomfortably generic, but given the semantics of "cache" gitignoring it seems a good idea.

ISTM rather than have every project add these to the project-specific gitignore this is really something every clang user should have in their personal gitignore for best effect. As long as they don't though, having the project do it will avoid inadvertantly git-adding these objects.

Steve