Passing environment variables to bst shell

Using https://gitlab.gnome.org/albfan/glade.git, branch buildsstream

cd bst
bst build --track-all glade.bst
bst shell glade.bst /usr/bin/glade

I get a:

(glade:3): Gtk-WARNING **: cannot open display:

I can fix it doing:

bst shell
DISPLAY=:0.0 glade

but is there any way to pass env var to bst shell. I tried

DISPLAY=:0.0 bst shell glade.bst /usr/bin/glade
bst shell glade.bst DISPLAY=:0.0 /usr/bin/glade
bst shell glade.bst "DISPLAY=:0.0 /usr/bin/glade"

but none works