Bootstrap environment modules optimizing for generic architectures (#13105)

fixes #13073

Since #3206 was merged bootstrapping environment-modules was using the architecture of the current host or the best match supported by the default compiler. The former case is an issue since shell integration was looking for a spec targeted at the host microarchitecture.

1. Bootstrap an env modules targeted at generic architectures
2. Look for generic targets in shell integration scripts
3. Add a new entry in Travis to test shell integration

.travis.yml

@@ -22,6 +22,11 @@ jobs:
       os: linux
       language: python
       env: TEST_SUITE=flake8
+# Shell integration with module files
+    - python: '3.7'
+      os: linux
+      language: python
+      env: [ TEST_SUITE=bootstrap ]
     - stage: 'unit tests + documentation'
       python: '2.6'
       dist: trusty