Ruledit window icon not in data of installed freeciv
Recently committed #43553 assumes that ruledit window icon can be found from FREECIV_DATA_PATH. While it is in data directory in the source tree, it gets installed under .../share/pixmaps.
Similar implementation for Qt fcmp icon in #44002 suffers from the same.
Attached patch should fix this, though I'm yet to test it properly.
Patch accidentally removes setting RULEDITDIRS.
- RULESETDIRS set correctly