compile-commands.json generator doesn't reflect PWD for "directory" attribute

[alicetrifu]

When generating compile-commands.json the "directory" attribute is always set to the root of the project which does not always reflect the working directory used during build. This means that relative file paths used in options (e.g. include paths), do not resolve in that particular cases.

Should confirm the behaviour of the working directory for managed make builds and ensure we're setting the attribute appropriately.

[jonahgraham]

Thank you @alicetrifu for this fix.