Smoke testing of xSDK packages with Spack

[shuds13]

Discuss whether packages should be required to invoke smoke testing via Spack.

Reference: The previous installation policy 12 stated:

12. After packages are configured, they can be compiled, installed and "smoke" tested with the following commands: `make ;

[sudo] make install ; make test_install`.

There is a run_tests option in Spack which can be invoked:

spack install --run-tests

The package support for this option is described in the Spack docs

As stated in the docs, a test function should be created with the special decorators. Some packages implement this, with different function names, some using the decorators and some just accessing self.run_tests such as hypre and petsc.

For packages that use the decorators, some use @run_after('build') as in the docs, some using @run_after('install') such as hdf5.

We should also discuss how this would work with the metapackage.