Tests ~ echo has portability issues; for CI, replace with printf

- using `echo` on 'windows' platforms requires process execution indirectly via the shell
- `printf` is available on all GHA CI platforms
  - `printf` is *not* available on usual 'windows' platforms; so this is just temporizing, awaiting a true fix

tests/examples/bat.conf

@@ -2,4 +2,4 @@
 --paging=always
 
 # Output a dummy message for the integration test.
---pager="echo dummy-pager-from-config"
+--pager="printf dummy-pager-from-config"