GMic: various fixes for CI
This MR fixes the bits that @rempt noticed in CI:
- Linux: Work around Launchpad PPA build script using "krita" as the library prefix
- Windows: Pre-create the downloads dir at Krita build time
macOS and AppImages are unaffected.
Test Plan
Although I have tested this with both the AppImage script and the Windows cmd, this needs CI to be extra sure.
Formalities Checklist
-
I confirmed this builds. -
I confirmed Krita ran and the relevant functions work. -
I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!) -
I made sure my commits build individually and have good descriptions as per KDE guidelines. -
I made sure my code conforms to the standards set in the HACKING file. -
I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.