Use CMake find_package for OpenSSL

[geedo0]

Context and motivation

The Amazon Linux aws-lc RPM spec could not build the provider as a subpackage. AWSLC_PROVIDER_OPENSSL_ROOT was an install prefix, so a distro passing /usr/include had it searched as /usr/include/include, and the provider had no install() rule, so a %files entry for the module could never be satisfied.

Description of changes

• OpenSSL is found through CMake's find_package(OpenSSL). AWSLC_PROVIDER_OPENSSL_ROOT is removed in favor of the standard OPENSSL_ROOT_DIR hint. Unset, system paths are searched, which is the openssl-devel case.
• OPENSSL_ROOT_DIR is treated as exclusive on every CMake. FindOpenSSL honors the root exclusively only on recent CMake. On 3.22 it falls back to system paths and skips lib64, which compiled the provider against pinned 3.5 headers while linking the system 3.0 libcrypto. When the root is set, the provider resolves the include directory and libcrypto under it first and fails if either is missing.
• The 3.5 version floor reads OPENSSL_VERSION from FindOpenSSL. The previous OPENSSL_VERSION_STR regex could not reject AWS-LC's own headers, which define only the hex number.
• The module installs to ${CMAKE_INSTALL_LIBDIR}/ossl-modules, overridable through the new AWSLC_PROVIDER_MODULESDIR cache variable. It is relative, so --prefix and DESTDIR work, and it matches OpenSSL's own default modules directory.

Testing

• Provider CI, both FIPS axes, through tests/ci/run_aws_lc_provider_tests.sh, which now passes -DOPENSSL_ROOT_DIR.
• The real aws-lc-5.2.0-2.amzn2027 spec with a provider subpackage builds aws-lc-provider, which owns /usr/lib64/ossl-modules/awslc.so and picks up libcrypto-awslc.so.1(AWS_LC_1.0) as an automatic requirement.

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.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.71%. Comparing base (8080fe6) to head (e7b1674).

Additional details and impacted files

@@                  Coverage Diff                  @@
##           feat/provider-errors    #3662   +/-   ##
=====================================================
  Coverage                 78.71%   78.71%           
=====================================================
  Files                       705      705           
  Lines                    130757   130757           
  Branches                  17922    17923    +1     
=====================================================
  Hits                     102920   102920           
- Misses                    26857    26858    +1     
+ Partials                    980      979    -1     

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[github-actions]

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