openssl: add a simple smoke test for the legacy provider

[ngie]

Summary

This change adds a simple smoke test for the legacy provider to ensure
that the provider doesn't break in the future when performing updates.

This is not a functional or system test; the OpenSSL test suite does a
much better job at doing this than we can.

MFC after: 1 month

Test Plan

$ kyua test -k /usr/tests/secure/lib/libcrypto/Kyuafile 
libcrypto_test:legacy_provider  ->  passed  [0.022s]

Results file id is usr_tests_secure_lib_libcrypto.20251012-041436-984512
Results saved to /home/ngie/.kyua/store/results.usr_tests_secure_lib_libcrypto.20251012-041436-984512.db

1/1 passed (0 broken, 0 failed, 0 skipped)

[glebius]

Does OpenSSL just picks up openssl.conf from current directory?

[ngie]

In D53045#1212112, @glebius wrote:

Does OpenSSL just picks up openssl.conf from current directory?

The test uses OPENSSL_CONF to specify the test config file.

From https://docs.openssl.org/3.0/man5/config/#environment :

OPENSSL_CONF

The path to the config file, or the empty string for none. Ignored in set-user-ID and set-group-ID programs.

[glebius]

In D53045#1212125, @ngie wrote:

The test uses OPENSSL_CONF to specify the test config file.

Sorry, I was blind.

[ngie]

In D53045#1212147, @glebius wrote:

In D53045#1212125, @ngie wrote:

The test uses OPENSSL_CONF to specify the test config file.

Sorry, I was blind.

No worries -- it's easy to miss in the "noise".