Use llvmpipe

recipes/mesa/recipe.sh

 GIT=https://gitlab.redox-os.org/redox-os/mesa.git
 GIT_UPSTREAM=git://anongit.freedesktop.org/mesa/mesa
 GIT_BRANCH=redox
-BUILD_DEPENDS=(expat zlib)
+BUILD_DEPENDS=(expat llvm zlib)
 
 function recipe_version {
     printf "r%s.%s" "$(git rev-list --count HEAD)" "$(git rev-parse --short HEAD)"
@@ -31,7 +31,7 @@ function recipe_build {
         --disable-glx \
         --disable-gbm \
         --disable-llvm-shared-libs \
-        --disable-llvm \
+        --enable-llvm \
         --enable-gallium-osmesa \
         --with-gallium-drivers=swrast \
         --with-platforms=surfaceless