Summary:
Passing an absolute project path as buck config flag makes buck caching almost impossible for infer artefacts, since on every host/run that directory can be different.
Eliminate that and rely on shell commands to find the project root, executed within the genrule.
Reviewed By: jvillard
Differential Revision: D15963807
fbshipit-source-id: b6e590029
Nikos Gorogiannis