Fix Python hermetic toolchain issue and improve test script

Author: davireis

projects/envoyproxy.io/package.yml

@@ -40,10 +40,13 @@ build:
       - --curses=no
       - --verbose_failures
       - --define=wasm=disabled
+      - --extra_toolchains=@rules_python//python:non_hermetic_toolchain
 
 provides:
   - bin/envoy
 
 test:
-  - envoy --version | grep {{version}}
-  - envoy --help
+  script:
+    - envoy --version | grep "envoy version"
+    - envoy --version | grep {{version}}
+    - envoy --help | grep "Usage"