[DRAFT] aws-lc-sys: avoid building unnecessary source files

[justsmth]

Description of changes:

• Avoid compiling AWS-LC source files not needed by aws-lc-rs.
• Reduces build latency of aws-lc-sys by between 20-40%.

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 92.86%. Comparing base (c358484) to head (3e52303).
Report is 184 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #711      +/-   ##
==========================================
- Coverage   95.80%   92.86%   -2.94%     
==========================================
  Files          61       70       +9     
  Lines        8143     9559    +1416     
  Branches        0     9559    +9559     
==========================================
+ Hits         7801     8877    +1076     
- Misses        342      413      +71     
- Partials        0      269     +269     

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