add AWS_LC_SYS_NO_JITTER_ENTROPY=1 to release musl build step to unblock releases (#12720)

linux musl build steps in `rust-release.yml` are [currently
broken](https://github.com/openai/codex/actions/runs/22367312571)
because of linking issues due to ubsan-calling types (`jitterentropy`)
leaking into the build.

add `AWS_LC_SYS_NO_JITTER_ENTROPY=1` to the musl build step to avoid
linking those ubsan-calling types. this is a more temporary fix, we need
to clean up ubsan usage upstream so they dont leak into release-build
steps anyways.

codex's more thorough explanation below:

[pr 9859](https://github.com/openai/codex/pull/9859) added [MITM
init](https://github.com/openai/codex/pull/9859/changes#diff-db782967007060c5520651633e1ea21681d64be21f2b791d3d84519860245b97R62-R68)
in network-proxy, which wires in cert generation code (rcgen/rustls).
this didnt bump/change dep versions, but it changed symbol reachability
at link time.

for musl builds, that made aws-lc-sys’s jitterentropy objects get pulled
into the final link. those objects contain UBSan calls
(__ubsan_handle_*). musl release linking is static (*-linux-musl-gcc,
-nodefaultlibs) and does not link a musl UBSan runtime, so link fails
with undefined __ubsan_*.

before, our custom musl CI UBSan steps (install libubsan1, RUSTC_WRAPPER
+ LD_PRELOAD, partial flag scrubbing) masked some sanitizer issues.
after this pr, more aws-lc code became link-reachable, and that band-aid
wasn't enough.

.github/workflows/rust-release.yml

@@ -178,6 +178,12 @@ jobs:
         shell: bash
         run: |
           set -euo pipefail
+          # Avoid problematic aws-lc jitter entropy code path on musl builders.
+          echo "AWS_LC_SYS_NO_JITTER_ENTROPY=1" >> "$GITHUB_ENV"
+          target_no_jitter="AWS_LC_SYS_NO_JITTER_ENTROPY_${{ matrix.target }}"
+          target_no_jitter="${target_no_jitter//-/_}"
+          echo "${target_no_jitter}=1" >> "$GITHUB_ENV"
+
           # Clear global Rust flags so host/proc-macro builds don't pull in UBSan.
           echo "RUSTFLAGS=" >> "$GITHUB_ENV"
           echo "CARGO_ENCODED_RUSTFLAGS=" >> "$GITHUB_ENV"