Fixes:
STM32CubeMX uses an outdated version of xstream that is not
compatible with JDK16. The derivation uses JDK11 (LTS) explicitly now.
Additionally, the desktop file wasn't generated by copyDesktopItems
before. This is now fixed as well.
Upstream changes:
- Main files moved from . to MX
- JAR file has no .exe extension anymore
- Icon format changed from icns to ico
- There is now a bundled JRE, but we prefer not to use it
Additional changes:
- Move version definition into mkDerivation
