[gnome-build-meta/valentindavid/update-local-repo-bst] utils/update-local-repo.sh: Allow overriding bst base command

[Valentin David <valentindavid src gnome org>]

commit b2a900591d9d40bb43b8d5975fe2cb9c7db1b8f3
Author: Valentin David <valentin david codethink co uk>
Date:   Wed Apr 21 09:58:56 2021 +0200

    utils/update-local-repo.sh: Allow overriding bst base command
    
    This is useful when needing to pass options to BuildStream. For
    example which architecture.

 utils/update-local-repo.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/utils/update-local-repo.sh b/utils/update-local-repo.sh
index ca71cf5c..ff4dfe84 100755
--- a/utils/update-local-repo.sh
+++ b/utils/update-local-repo.sh
@@ -2,7 +2,7 @@
 
 set -eu
 
-BST=bst
+: ${BST:=bst}
 REPO_ELEMENTS=''
 
 while [ $# -gt 0 ]; do