Make KCrash optional
When developing it can be useful to let system generate a coredump which can be debugged very easily with gdb
.
Currently you can do that by exporting KDE_DEBUG=1
but sometimes it can be better to disable KCrash/DrKonqi altogether.
Now with this MR can specify cmake -DCMAKE_DISABLE_FIND_PACKAGE_KF5Crash=ON
to build without KCrash.
I personally always have been exporting KDE_DEBUG=1
globally system wide and never want DrKonqi since I want to be able to interactively debug crashes.