Specify a default shell for run steps

This should help debugging as any interpolated values will now appear
in the log.

.github/workflows/build.yml

@@ -24,6 +24,14 @@ on:
         required: true
         default: "dispatch"
 
+# Set a default shell for any run steps. The `-Eueo pipefail` sets errtrace,
+# nounset, errexit, and pipefail. The `-x` will print all commands as they are
+# run. Please see the GitHub Actions documentation for more information:
+# https://docs.github.com/en/actions/using-jobs/setting-default-values-for-jobs
+defaults:
+  run:
+    shell: bash -Eueo pipefail -x {0}
+
 env:
   BUILDX_CACHE_DIR: ~/.cache/buildx
   CURL_CACHE_DIR: ~/.cache/curl