bin/bwrap: exit if not on Linux and source bwrap extra

bin/bwrap.bash

@@ -1,5 +1,9 @@
 #!/usr/bin/env bash
 
+if [ "$(uname)" != "Linux" ]; then
+  exit 0
+fi
+
 if [ -z ${NIXDIR+x} ]; then 
     echo "NIXDIR is unset! It needs to be set in the code. Edit this shell file and read the instructions."
     echo "Executing bash without Bubblewrap…"
@@ -58,4 +62,6 @@ devbind \
     /usr \
     /var
 
+[[ -f "$HOME/.bwrap-extra.bash" ]] && source "$HOME/.bwrap-extra.bash"
+
 exec bwrap "${args[@]}" "$@"