Add Clang support on Windows for FIPS shared build

[aminya]

Issues:

Fixes #2981

Description of changes:

This fixes building aws-lc on Windows when using Clang as the compiler.

Instead of using the non-supported linker flags with clang on Windows, the bcm compilation is handled with the correct flags and markers

Call-outs:

N/A minor build change

Testing:

Build with Cmake or Cargo as normal

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.

[justsmth]

Hello! Thanks for the PR!

We have a CI workflow for testing alternative (non-MSVC) compilers on Windows. With this change, should we be able to add a "FIPS" variant for the clang jobs in this workflow?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.34%. Comparing base (0628190) to head (7751e94).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2982      +/-   ##
==========================================
- Coverage   78.35%   78.34%   -0.01%     
==========================================
  Files         689      689              
  Lines      121010   121010              
  Branches    16992    16992              
==========================================
- Hits        94813    94802      -11     
- Misses      25302    25313      +11     
  Partials      895      895              

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[aminya]

Hello! Thanks for the PR!

We have a CI workflow for testing alternative (non-MSVC) compilers on Windows. With this change, should we be able to add a "FIPS" variant for the clang jobs in this workflow?

Hi, you're welcome!

I created a PR for the addition of CI jobs:
#2984 (comment)

P.S: I'd rather keep the CI PR separate, as making it work requires some work.

[justsmth]

P.S: I'd rather keep the CI PR separate, as making it work requires some work.

Yeah, I've been trying to make the tests pass but am not having much luck so far. I combined the two PRs b/c the tests on the 2nd PR are needed to confirm that the first PR's changes are correct. I'll keep poking at this change till the tests pass.

[aminya]

P.S: I'd rather keep the CI PR separate, as making it work requires some work.

Yeah, I've been trying to make the tests pass but am not having much luck so far. I combined the two PRs b/c the tests on the 2nd PR are needed to confirm that the first PR's changes are correct. I'll keep poking at this change till the tests pass.

Thanks. The build is successful, which is great.
My use case (Rustls) doesn't need FIPs, but the build failure was problematic.