Minor build fixes for CMake and libssl on x86

[skmcgrail]

Description of changes:

• Removes unnecessary variable evaluation in a handful of if statements for CMAKE_SYSTEM_PROCESSOR_LOWER. These can result in a failure if CMAKE_SYSTEM_PROCESSOR_LOWER is an empty string as the ${} is expanded first in the if-statement due to historical reasons.
• libssl can fail to compile if building on x86 since we don't pass -msse2 to the C++ compiler. This is due to the fact that the crypto/internal.h is included by libssl and it explicitly checks for SSE2 support. See https://github.com/aws/aws-lc/blob/main/crypto/internal.h#L203-L214

Testing

• Verified build with a modified ./util/32-bit-toolchain.cmake that only sets -m32 (since building on an x86-64 platform).

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 79.04%. Comparing base (8d77e4c) to head (d757ad7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2267      +/-   ##
==========================================
- Coverage   79.04%   79.04%   -0.01%     
==========================================
  Files         612      612              
  Lines      106588   106630      +42     
  Branches    15083    15098      +15     
==========================================
+ Hits        84252    84281      +29     
- Misses      21684    21696      +12     
- Partials      652      653       +1     

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