Work around test -v not being available in Mac Bash

.github/workflows/__go-reconciled-tracing-custom-build-steps.yml

@@ -93,7 +93,10 @@ jobs:
         TEST_MODE: true
     - shell: bash
       run: |
-        if [[ -v CODEQL_ACTION_DID_AUTOBUILD_GOLANG ]]; then
+        # Once we start running Bash 4.2 in all environments, we can replace the
+        # `! -z` flag with the more elegant `-v` which confirms that the variable
+        # is actually unset and not potentially set to a blank value.
+        if [[ ! -z "${CODEQL_ACTION_DID_AUTOBUILD_GOLANG}" ]]; then
           echo "Expected the Go autobuilder not to be run, but the" \
             "CODEQL_ACTION_DID_AUTOBUILD_GOLANG environment variable was set."
           exit 1