In Qt version 5.15.0 moc learned to output the dependencies
of the generated file.
This commit enhances JobCompileMocT to read the dependency file
written by moc. The dependencies are stored in the same cache that's
used for the dependencies determined by dependency filters.
The dependency filter functionality is turned off if moc's dependency
output feature is used.
Fixes: #17750Fixes: #19058
f765fdea03