Update aws-lc-sys, align w/ AWS-LC v1.34.2

[justsmth]

Description of changes:

• Aligns aws-lc-sys v0.21.0 w/ AWS-LC v1.34.2
  • Adds support for a AWS_LC_SYS_C_STD environment variable to determine which C standard to use.
  • For platforms that build using "cc" (instead of CMake), the build defaults to using the C11 standard.

Call-outs:

• Automated workflow is here: https://github.com/aws/aws-lc-rs/actions/runs/10598652101
• Only first commit is manual.
• The C11 build doesn't contain the CRYPTO_refcount_dec_and_test_zero or CRYPTO_refcount_inc symbols. We need these symbols to be prefixed for C99 build. Thus, for some targets in the symbol collection step of the automation are being forced to use a C99 build.

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 (99c6931).
Report is 78 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #509      +/-   ##
==========================================
- 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     

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

[andrewhop]

If it's something we can't parse should this be a hard error? If someone set AWS_LC_SYS_C_STD=c11 it would hit none here, and then could they actually get c99, or vice versa.

[justsmth]

Yeah, I thought about matching against a RegExp here to add more flexibility, but I'm not sure it's worth the trouble.

I see this environment variable as something that will rarely be needed. We will default to C11 for most consumers (which should work for any build host that's been setup sometime in the last decade).

[zh-jq]

Is it possible to update bindgen to 0.70 for aws-lc-sys v0.21.0?

[justsmth]

Is it possible to update bindgen to 0.70 for aws-lc-sys v0.21.0?

Unfortunately, bindgen v0.70.x has an MSRV of 1.70, whereas our crates still maintain an MSRV of 1.63. (Our current dependency is on bindgen v0.69.4 which has an MSRV of 1.60.)

When we update our MSRV again, we plan to also update many of our dependencies to more recent versions.