Muflone  filed a orphan request for msbuild-15-bin :
the package is out of date since long time. a more up-to-date package exists https://aur.archlinux.org/packages/msbuild-15.3-bin/ which can be merged with this one
 https://aur.archlinux.org/account/Muflone/  https://aur.archlinux.org/pkgbase/msbuild-15-bin/
Request #10982 has been accepted by Eschwartz :
current maintainer adopted it but never updated it, sort of odd...