fix(gentoo): add inherit xdg-utils to qbz-bin ebuild template

pkg_postinst and pkg_postrm in the binary ebuild call
xdg_icon_cache_update and xdg_desktop_database_update, which
come from the xdg-utils eclass. Without `inherit xdg-utils`
those helpers are undefined and the hicolor icon cache never
refreshes on upgrade.

The source ebuild template (qbz.ebuild.template) already
inherits xdg, so this only affects users installing via
qbz-bin (the prebuilt binary path). The qbz-overlay has a
direct patch for v1.2.5; this ensures v1.2.6+ release-gentoo
runs emit correct ebuilds.

cc

packaging/gentoo/qbz-bin.ebuild.template

@@ -3,6 +3,8 @@
 
 EAPI=8
 
+inherit xdg-utils
+
 DESCRIPTION="Native hi-fi Qobuz desktop player for Linux (prebuilt binary)"
 HOMEPAGE="https://qbz.lol https://github.com/vicrodh/qbz"