installer :script should make its target executable in advance

[vitorgalvao]

Just came across this while working on anaconda. The installer :script target wouldn’t run due to it not having permission to execute. set_permissions doesn’t work to fix this because the soonest it’s available is postflight, and this needed to be preflight. The old way had to be used.

Either way, it should be the responsibility of installer :script to make sure its target can be run.

[jawshooah]

While I agree with making installer scripts executable by default, I think the set_permissions and set_ownership methods should be available in the preflight block regardless. PR incoming.