devel/alire: Update to 2.1.0

Update to 2.1.0:

• Integrate tests
• Remove ${USE_GCC} build requirement
• Remove hard-corded version 12 (ada) from ${USES}
• Remove desktop-file-utils from ${USES}, because no MIME type is declared
• Remove pkg-plist, replacing its contents with the dynamically generated ${PLIST_FILES}, and ${PORTDOCS}
• Replace DEBUG option with dynamic ${WITH_DEBUG:Undefined:Defined} Makefile substitution. This removes the if conditional, and <bsd.port.options.mk>
• Set ${MAINTAINER} to william.franck@sterna.dev.
• Some port{clippy|fmt|lint} maintenance
• Use ${MAKE_CMD} in the do-build target instead of hard-coding grpbuild

https://github.com/alire-project/alire/releases/tag/v2.1.0

PR: 277852
Co-authored-by: Marcin Cieślak <saper@saper.info>