[clang-tools-extra] [clang] In compilation databases, add support for relative directories (PR #69856)

[via cfe-commits]

Overhatted wrote:

The use-case is the example project here: https://github.com/facebook/buck2/pull/517

The documentation update was done here: https://github.com/llvm/llvm-project/pull/69856/commits/7a92e0a3996ea3f518b6c3d740e1122902668308#diff-33e467b29775682c8ee8d50375fcabec58ebe215acebf15151f451a82b9c5e67 which I think is the only place requiring an update.

For the moment I'm passing in the workspace folder to the Buck2 script generating the compilation database which is a good workaround. But I think this would be a nice feature either way.

I wanted this to work on Windows as well and I don't know of a workaround similar to "/proc/self/cwd" on Windows.

Let me know what you think.

https://github.com/llvm/llvm-project/pull/69856