This removes resource forks from our template disk image. Add custom InstallWithSymLinks command that does behave similar to the default env.Install command, however preserves relative symbolic links inside an installed directory. This is needed because the Sparkle.framework internally uses symbolic links and codesign utility fails if these links are replaced by copies of the original files. Test-Information: Verified dist=1 builds with and without code signing on macOS 10.12. Verified that on change of presence of the codesign_identity SCons argument or its value, a new package is build. If it does not change nothing is built again. Change-Id: Iade94811b7d608cb7520662e2820be3b128ee90b