This build failure happens during a metro build and is related to finding a suitable llvm version:
* Messages for package media-libs/mesa-20.2.4-r1: * ERROR: media-libs/mesa-20.2.4-r1::core-gl-kit failed (setup phase): * No LLVM slot <= 11 found installed! * * Call stack: * ebuild.sh, line 93: Called pkg_setup * mesa-20.2.4-r1.ebuild, line 328: Called llvm_pkg_setup * llvm.eclass, line 201: Called get_llvm_prefix '11' * llvm.eclass, line 180: Called die * The specific snippet of code: * die "No LLVM slot${1:+ <= ${1}} found installed!" *