Fix pregeneration of bindings

[justsmth]

Description of changes:

• Rename environment variable to remove ambiguity: AWS_LC_SYS_INTERNAL_BINDGEN -> AWS_LC_SYS_PREGENERATING_BINDINGS
  • Rename associated (internal function): is_internal_bindgen() -> is_pregenerating_bindings()
• Include aws-lc-fips-sys in our pregen-binding.yml CI workflow.
• The generated-include directory should not be included when performing a no-prefix build
• Cleanup the compiler_check logic.
• Generate additional diagnostic warnings during build.

Testing:

• aws-lc-sys bindings workflow tested here: https://github.com/aws/aws-lc-rs/actions/runs/11073978233
• aws-lc-fips-sys bindings workflow tested here: https://github.com/aws/aws-lc-rs/actions/runs/11073987388

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 92.52%. Comparing base (c358484) to head (fe43a79).
Report is 84 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #541      +/-   ##
==========================================
- Coverage   95.80%   92.52%   -3.28%     
==========================================
  Files          61       67       +6     
  Lines        8143     9277    +1134     
  Branches        0     9277    +9277     
==========================================
+ Hits         7801     8584     +783     
- Misses        342      422      +80     
- Partials        0      271     +271     

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