fix(spread-24.04): make spread work on armhf (#370)

This fixes an error where spread tests on docker for armhf was failing
the preparation step due to getting both the arm and arm64 downloads.

spread.yaml

@@ -87,7 +87,7 @@ prepare: |
 
   apt install -y curl wget
   curl -s https://api.github.com/repos/canonical/chisel/releases/latest \
-    | awk "/browser_download_url/ && /chisel_v/ && /$arch/" \
+    | awk "/browser_download_url/ && /chisel_v/ && /_$arch\./" \
     | cut -d : -f 2,3 \
     | tr -d \" \
     | xargs wget

tests/spread/integration/dash/task.yaml

@@ -0,0 +1,8 @@
+summary: Integration tests for dash
+
+execute: |
+  rootfs="$(install-slices dash_bins)"
+
+  chroot "${rootfs}" dash -c "echo Success > /test"
+
+  test $(cat "${rootfs}/test") == "Success"