fix: ensure all build flags are consumed as an array

tests/unit/builder-lambda.bats

@@ -134,6 +134,34 @@ teardown() {
   assert_success
 }
 
+@test "(builder-lambda) run" {
+  run /bin/bash -c "dokku config:set $TEST_APP SECRET_KEY=fjdkslafjdk"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku builder:set $TEST_APP selected lambda"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run deploy_app python dokku@$DOKKU_DOMAIN:$TEST_APP inject_lambda_yml
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku ps:inspect $TEST_APP"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku run $TEST_APP env"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output_contains "SECRET_KEY=fjdkslafjdk"
+}
+
 inject_lambda_yml() {
   local APP="$1"
   local APP_REPO_DIR="$2"