Add fallback to our mesa package for non-NixOS hosts

munix

@@ -15,6 +15,10 @@ PIPEWIRE=1
 X11=0
 export TMP=/tmp TMPDIR=/tmp TEMP=/tmp TEMPDIR=/tmp LC_ALL=C
 
+if [ ! -e "$HOST_OPENGL_DRIVER" ]; then
+  HOST_OPENGL_DRIVER="$FALLBACK_OPENGL_DRIVER"
+fi
+
 while [ "$#" -gt 0 ]; do
   case "$1" in
     -u|--uid) MICROVM_UID="$2"; shift 2;;
@@ -58,6 +62,11 @@ if [ "$PASST_PATH" = "" ]; then
   exit 1
 fi
 
+if [ ! -e "$HOST_OPENGL_DRIVER" ]; then
+  echo "munix: host graphics driver not found, provide a --host-opengl-driver" >&2
+  exit 1
+fi
+
 # Resolve symlinks automatically
 MICROVM_CLOSURE=$(realpath "$MICROVM_CLOSURE")