Fix BSD shell inside the VM to be bash

.github/workflows/ci.yml

@@ -959,6 +959,10 @@ jobs:
             version: ${{matrix.bsd_version}}
             environment_variables: GIT_FETCH_JOBS NET_RETRY_COUNT DEFAULT_BUILD_VARIANT
             sync_files: false
+            # The 'run' script below uses bash arrays (DEPINST_ARGS / B2_ARGS), so the
+            # commands forwarded into the VM by cpa.sh must be executed with bash. Without
+            # this the BSD default /bin/sh that does not support the following syntax
+            shell: bash
 
         # Step 2: Run your commands inside the VM using the custom shell
         - name: Test on ${{matrix.vm}}