After JDK-8313374, out of tree incremental builds with ccache started failing. The rewriting of the generated dependency (*.d) files creates object file paths with `/../` in them which make does not match to other rules. I don't think we should apply the rewriting when the build dir is outside CCACHE_BASEDIR. That seems to fix the issue.

During review of JDK-8313374 I also noted that the CCACHE_BASEDIR should point to WORKSPACE_ROOT rather than TOPDIR for ccache to work uniformly for OracleJDK and OpenJDK builds.

I would like to address both of these issues with this bug.