testers.testBuildFailure: Fix

A call to getAllOutputNames was added as part of the structuredAttrs
effort, but this script does not source `setup.sh`, so I repeat the
definition here.
Should be a bit quicker than `source setup.sh`.

pkgs/build-support/testers/expect-failure.sh

@@ -35,6 +35,14 @@ echo "testBuildFailure: Original builder produced exit code: $r"
 # -----------------------------------------
 # Write the build log to the default output
 
+getAllOutputNames() {
+    if [ -n "$__structuredAttrs" ]; then
+        echo "${!outputs[*]}"
+    else
+        echo "$outputs"
+    fi
+}
+
 outs=( $(getAllOutputNames) )
 defOut=${outs[0]}
 defOutPath=${!defOut}