All includes coming from isystem where wrong as the regex was not able
to recognize that the isystem and following path belong together.
Additionally stripping the first two characters resulted in broken paths
in this case.

Change-Id: Iaa8e484d1ddcd4c8744d1e37a006ebf915cdfc84
Reviewed-on: https://gerrit.libreoffice.org/10815Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>