erasure-code: always compile SSE and NEON tests

They do not actually depend on CPU features and are required to validate
the plugin selection logic.

Signed-off-by: Loic Dachary <ldachary@redhat.com>
erasure-code: include new headers in distribution

The NEON optimization introduced new headers that must be listed
explicitly to be included in tarbals.

Signed-off-by: Loic Dachary <ldachary@redhat.com>
erasure-code: test NEON arch selection logic

The jerasure plugin loads the plugin that matches the architecture
supported by the CPU at runtime. Include the NEON plugin in the tests.

Signed-off-by: Loic Dachary <ldachary@redhat.com>