devel/qt6-base: Fix warnings with LLVM 19

Pushing and popping the pragma within the qcomparehelpers macros doesn't
seem to be working anymore with LLVM 19. Unwrap the pragma until a
better solution can be found.

This should get www/dooble building again on CURRENT and suppress many
useless warnings in other ports.

MFH: 2024Q4
(cherry picked from commit bfa2bdb1bbeea3e6377255d5bf530daed004bf72)