macos-bigsur-icon

The "ifdef" doesn't seem to be taken in account. It's as if the define was
always set. Now that the define is properly used we need to pass it to moc.

(cherry picked from commit 568aba0b) (edited)
edited:
- on 3.0 the files are not in a dialog subfolder

Signed-off-by: Steve Lhomme <robux4@ycbcr.xyz>