fix env variable

Author: sebsto

.github/workflows/integration_tests.yml

@@ -152,7 +152,7 @@ jobs:
           # TODO : add a similar test to Swift AWS Lambda Events
           EXAMPLE: APIGateway
           OUTPUT_DIR: .build/release
-          OUTPUT_FILE: ${OUTPUT_DIR}/APIGatewayLambda
+          OUTPUT_FILE: ${{ env.OUTPUT_DIR }}/APIGatewayLambda
           LIBS_TO_CHECK: "libFoundation.so libFoundationInternationalization.so lib_FoundationICU.so"
         run: |
           pushd Examples/${EXAMPLE}