Windows build: Add libheif to the system libraries check
This MR fixes the Windows build script to accept libheif's dependencies as non-system libraries. This lets the script build them in case meson, ninja, and rustc (AVIF support) are available.
Test Plan
Build 3rdparty deps.
Formalities Checklist
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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.