Author says build dependencies calculation is not common in free software world . Aren’t emerge and other systems in source based distributions like gentoo doi

Author says build dependencies calculation is not common in free software world . Aren’t emerge and other systems in source based distributions like gentoo doing this for 20 odd years now ? https://devmanual.gentoo.org/general-concepts/dependencies/ https://devmanual.gentoo.org/general-concepts/dependencies/ I don’t understand how the RDEPEND , BDEPEND setup doesn’t handle this, and the problem should be hardly unique for just rust ? Perhaps handling this in the package layer in a distribution not designed to handle build dependencies properly is the problem ?