No CMake required for non-FIPS

[justsmth]

Issues:

Addresses Issues:

• Support for building aws-lc-rs with just rustc  #152
• Remove CMake requirement for builds #297

Description of changes:

• Allow for non-FIPS build requiring only a C compiler.
• Extended existing bindgen automation to also collect require information for no-CMake build.
• Cleaned up build logic around platform detection.
• Re-aligned aws-lc-fips-sys builder/main.rs with aws-lc-sys.

Call-outs:

• The change allows the build to be performed w/o CMake on the same platforms for which we pre-generate the bindings: i686-unknown-linux-gnu, x86_64-unknown-linux-gnu, aarch64-unknown-linux-gnu, x86_64-unknown-linux-musl, aarch64-unknown-linux-musl, x86_64-apple-darwin, aarch64-apple-darwin
• The AWS_LC_SYS_CMAKE_BUILDER environment variable can be used to force the build to use, or not use, CMake.

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 95.82%. Comparing base (a29a615) to head (b6d06c8).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #317   +/-   ##
=======================================
  Coverage   95.82%   95.82%           
=======================================
  Files          60       60           
  Lines        7865     7865           
=======================================
  Hits         7537     7537           
  Misses        328      328           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[camshaft]

One thing to note that we need to replicate (and maintain) the build-time checks here:

https://github.com/aws/aws-lc/blob/37708f52446ee727ebeea6beaba75baf0588593b/CMakeLists.txt#L426-L430
https://github.com/aws/aws-lc/blob/37708f52446ee727ebeea6beaba75baf0588593b/CMakeLists.txt#L311-L317

[pronebird]

What do you refer to when you say FIPS? Federal Information Processing Standards? Apologize for being silly, not familiar with the abbreviation.

[justsmth]

Yeah, "FIPS" stands for "Federal Information Processing Standards". We perform a special build process for AWS-LC when the "fips" feature is enabled. There is more information and links in this blog post about it: https://aws.amazon.com/blogs/security/aws-lc-is-now-fips-140-3-certified/

[pronebird]

Does cmake have to be a part of build-dependencies?