If a test fails, it's possible to re-run just that specific test for that
specific backend using:

> make check-crypto-$backend XMLSEC_TEST_NAME="$name"

where $name is the key name for key tests, and a file name otherwise.

Example:

> make check-crypto-nss XMLSEC_TEST_NAME="enveloping-sha256-rsa-sha256-relationship"
