Pull request testing should set -Werror

Created by: mhoemmen

@vbrunini asks whether pull request testing could set -Werror, so as to avoid issues like #3177 (closed).

@trilinos/framework @khpierson

Expectations

Trilinos -- at least the library, not necessarily tests and examples -- should build warning-free.

Current Behavior

See #3177 (closed). There is an issue that it's impossible to fix warnings in some packages.

Motivation and Context

Sierra builds with warnings as errors, so they want Trilinos to build warning-free.

Possible Solution

Exclude legacy packages like ML. Fix warnings. Add -Werror to at least one PR build.

Related Issues

• Related to #3177 (closed)