Here is a summary of the failures.
With anything (tq)moc or (t)qmake related, grep your local source tree to ensure you are
updated. Some of those errors you posted have been patched. Look at the commit web page to
find those patches.
Check that you are not hard-coding anything in your build scripts. At one time or another
some of us were hacking our build scripts to force successful builds. We no longer need
those build script hacks as various problems are resolved.
The gtk3 thing is new to all of us. Slackware Current has not added gtk3. Therefore I
won't be able to test that. :-(
I started my build runs, but I have to attend to some chores and errands this afternoon.
I'll be away for a while. :-)
Darrell