Fix SSL_BUILD_CHAIN_FLAG_IGNORE_ERROR behavior

[samuel40791765]

Description of changes:

This was discovered when taking google/boringssl@5b3dc49 during the upstream merge.
ERR_clear_error is being called more eagerly with the new change, which led us to discover that SSLTest.BuildCertChain was actually testing against an error code propagated onto the stack by the previous call to SSL_CTX_build_cert_chain.

Upon further examination, we weren't propagating an error when calling SSL_CTX_build_cert_chain with SSL_BUILD_CHAIN_FLAG_IGNORE_ERROR . The correct behavior should be to push an error onto the stack regardless.

Call-outs:

N/A

Testing:

Slight test tweaks

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.08%. Comparing base (8258d73) to head (77da30f).
Report is 19 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1620      +/-   ##
==========================================
+ Coverage   78.05%   78.08%   +0.02%     
==========================================
  Files         562      562              
  Lines       94600    94656      +56     
  Branches    13575    13574       -1     
==========================================
+ Hits        73840    73908      +68     
+ Misses      20168    20153      -15     
- Partials      592      595       +3     

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