devel/qt5-buildtools: Hello 'L'-o

Add support for the 'L' integer suffix to moc.

This fixes a parsing bug that appeared in graphics/qt5-wayland after [1].
extensions/qwltexturesharingextension_p.h:145: Parse error at "DESIGNABLE"

Many thanks to kenrap and fuz for their help!

[1] https://cgit.freebsd.org/src/commit/?id=f441a225c4eb56deff1edc2402fe85a0ae263ebd

PR: 292531
Reported by: Kenneth Raplee <kenrap@kennethraplee.com>
MFH: 2026Q1