fix discarded-qualifiers warning

[toidiu]

Resolved issues:

resolves #ISSUE-NUMBER1, resolves #ISSUE-NUMBER2, etc.

Description of changes:

New version of clang as seeing new failures due to -Werror=discarded-qualifiers. This PR fixes those warnings.

make: warning: -j2 forced in submake: resetting jobserver mode.
  /home/runner/work/s2n-quic/s2n-quic/tls/s2n-tls-sys/s2n/crypto/s2n_rsa_pss.c: In function ‘s2n_evp_pkey_to_rsa_pss_public_key’:
  /home/runner/work/s2n-quic/s2n-quic/tls/s2n-tls-sys/s2n/crypto/s2n_rsa_pss.c:185:24: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
    185 |     RSA *pub_rsa_key = EVP_PKEY_get0_RSA(pkey);
        |                        ^~~~~~~~~~~~~~~~~
  /home/runner/work/s2n-quic/s2n-quic/tls/s2n-tls-sys/s2n/crypto/s2n_rsa_pss.c: In function ‘s2n_evp_pkey_to_rsa_pss_private_key’:
  /home/runner/work/s2n-quic/s2n-quic/tls/s2n-tls-sys/s2n/crypto/s2n_rsa_pss.c:195:25: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
    195 |     RSA *priv_rsa_key = EVP_PKEY_get0_RSA(pkey);
        |                         ^~~~~~~~~~~~~~~~~
  cc1: all warnings being treated as errors
  make[2]: *** [CMakeFiles/s2n.dir/build.make:356: CMakeFiles/s2n.dir/crypto/s2n_rsa_pss.c.o] Error 1
  make[2]: *** Waiting for unfinished jobs....
  make[1]: *** [CMakeFiles/Makefile2:3910: CMakeFiles/s2n.dir/all] Error 2
  make: *** [Makefile:146: all] Error 2
  thread 'main' panicked at '
  command did not execute successfully, got: exit status: 2

Call-outs:

Address any potentially confusing code. Is there code added that needs to be cleaned up later? Is there code that is missing because it’s still in development?

Testing:

How is this change tested (unit tests, fuzz tests, etc.)? Are there any testing steps to be verified by the reviewer?

Is this a refactor change? If so, how have you proved that the intended behavior hasn't changed?

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[tv-deusen]

I'm facing this issue trying to build a small program using s2n-quic v1.0. Are there any resolutions for this?

[camshaft]

This issue should be fixed by #3474. You'll need to update to s2n-quic 1.9.2 if you want to pick up the changes.

[tv-deusen]

It appears 1.9.2 still has the same issue for me.

[camshaft]

Can you open an issue in s2n-quic detailing your setup and the error message you're seeing?