Crosser-2.7

• Produced binaries now require Windows 8.1 by default
• Cross pkg-config is installed under native tree on dllstack package
• Properly use pkgconf also as the cross-tool when so configured
• Renamed configure option DLLSHOST_PREFIX as CROSSER_HOST_PREFIX
• Builder container improvements:

• Container updated to Debian Bookworm
• Container supports building versionsets other than "current"
• Container supports building for other "setup" than the default
• Container output directory provides access to host-side builds

• Updated gtk4 to version 4.10
• Updated qt6 to version 6.5