(In reply to roland@rptd.ch from comment #9)
> I get two config attempts. This is the second one. Do you see anything out
> of place here?
> 
> meson --buildtype plain --libdir lib64 --localstatedir /var/lib --prefix
> /usr --sysconfdir /etc --wrap-mode nodownload
> -Dplatforms=x11,surfaceless,wayland,drm -Dllvm=true -Dlmsensors=true
> -Dlibunwind=false -Dgallium-nine=false -Dgallium-va=false
> -Dgallium-vdpau=false -Dgallium-xa=false -Dgallium-xvmc=false
> -Dgallium-opencl=icd -Dosmesa=none -Dbuild-tests=false -Dglx=dri
> -Dshared-glapi=true -Ddri3=true -Degl=true -Dgbm=true -Dgles1=false
> -Dgles2=true -Dglvnd=false -Dselinux=false -Dvalgrind=false
> -Ddri-drivers=r100,r200 -Dgallium-drivers=r300,r600,radeonsi,swrast
> -Dvulkan-drivers=amd --buildtype plain -Db_ndebug=true
> /var/tmp/portage/media-libs/mesa-19.0.8/work/mesa-19.0.8
> /var/tmp/portage/media-libs/mesa-19.0.8/work/mesa-19.0.8-abi_x86_64.amd64

Just change the /var/tmp/portage/... path to your own build directory and you
should be good :)