diff_spec: Fix paths comparisons on Windows
diff_spec: Fix paths comparisons on Windows

On Windows the paths are prefixed with "C:". Fix this in a generic way by
explicitly making them absolute.

sschuberth/LicenseFinder,bdshroyer/LicenseFinder,pivotal/LicenseFinder,pivotal/LicenseFinder,pivotal/LicenseFinder,bspeck/LicenseFinder,joemoore/LicenseFinder,pivotal/LicenseFinder,bdshroyer/LicenseFinder,bspeck/LicenseFinder,bdshroyer/LicenseFinder,joemoore/LicenseFinder,tinfoil/LicenseFinder,tinfoil/LicenseFinder,joemoore/LicenseFinder,sschuberth/LicenseFinder,tinfoil/LicenseFinder,bspeck/LicenseFinder,bdshroyer/LicenseFinder,tinfoil/LicenseFinder,joemoore/LicenseFinder,pivotal/LicenseFinder,bspeck/LicenseFinder,joemoore/LicenseFinder,sschuberth/LicenseFinder,tinfoil/LicenseFinder,sschuberth/LicenseFinder,pivotal/LicenseFinder,sschuberth/LicenseFinder,pivotal/LicenseFinder,bdshroyer/LicenseFinder,bspeck/LicenseFinder