Relative Paths in Compilation Database

Looks good.

Hey all,

This sounds like a good development, and I’d like to throw in my 2 cents.

I looked at a related problem before, and I think it boils down to the
same challenge – Manuel and I discussed it on the bug here:
http://llvm.org/bugs/show_bug.cgi?id=19687

I ran out of steam before I got around to any real implementation, but
I think the primary challenge is that CMake and Ninja (or other
compdb-producers) don’t necessarily have the arguments in list form
either. They usually seem to just have a command-line.

Which should be fine if we allow both.

So the complexity of splitting the command-line into arguments can
either go in all the world’s generators, or in the single consumer in
LibTooling.

Or we add a little complexity to libtooling to allow both.