feat: Use sandbox name directly in creation of image script

* adds support for multiple sandboxes being present

Change-Id: I1556af0a09e1543a9d07131ae6ea1dd8baafcf05

lib/yashchiki/build_image.sh

@@ -3,12 +3,7 @@
 set -euo pipefail
 shopt -s inherit_errexit 2>/dev/null || true
 
-if (( $(find ${YASHCHIKI_SANDBOXES} -mindepth 1 -maxdepth 1 | wc -l) > 1 )); then
-    echo "More than one sandbox found, this should never happen!" >&2
-    exit 1
-fi
-
-TARGET_FOLDER="$(find ${YASHCHIKI_SANDBOXES} -mindepth 1 -maxdepth 1)"
+TARGET_FOLDER="${YASHCHIKI_SANDBOXES}/${CONTAINER_STYLE}"
 
 # We want the spack folder to be available inside the container image
 # -> it needs to be bind mounted to the sandbox folder