What's the status on making BUILDENV extendable?I've been using pacman-buildenv_ext-git very successfully for quite some time now.
https://aur.archlinux.org/cgit/aur.git/tree/buildenv_ext.patch?h=pacman-buildenv_ext-gitpacman-buildenv_ext-git can even be used to build packages with pgo, graphite, and lto in a "clean" chroot. I do this very often, it works (so long as the software being packaged itself can be safely optimized in those ways).
