Unblock aws-lc-sys cross-compile in CI

The new bpi rev pulled reqwest 0.13, whose `rustls` feature forces
aws-lc-rs as the rustls crypto provider via cargo feature unification.
aws-lc-sys then has to cross-compile its bundled C, which the napi-rs
docker images can't do out of the box:

- x86_64-unknown-linux-gnu: aws-lc-sys probes the compiler with
  -fuse-ld=lld and the image has no lld installed.
- aarch64-unknown-linux-gnu: the image pre-sets CC_aarch64_unknown_linux_gnu
  and CFLAGS pointing at its custom cross toolchain under
  /usr/aarch64-unknown-linux-gnu, whose sysroot is missing stdatomic.h.
  The previous exports just sat alongside the docker's values without
  overriding them, so aws-lc-sys was still picking up the broken sysroot.

Install lld and, on aarch64, unset the inherited env before exporting
the Debian cross toolchain values so they actually take effect.

This is the smallest fix that keeps rustls in place. The alternative
was patching bpi to use reqwest's `rustls-no-provider` plus an explicit
ring provider, which would have required a runtime
CryptoProvider::install_default() call and another upstream fork bump.

Author: amackillop

.github/workflows/CI.yml

@@ -71,6 +71,9 @@ jobs:
             target: x86_64-unknown-linux-gnu
             docker: ghcr.io/napi-rs/napi-rs/nodejs-rust:lts-debian
             build: |
+              set -e
+              apt-get update
+              apt-get install -y lld
               rustup install $RUST_VERSION
               rustup default $RUST_VERSION
               rustup target add x86_64-unknown-linux-gnu
@@ -94,7 +97,16 @@ jobs:
             build: |
               set -e
               apt-get update
-              apt-get install -y gcc-aarch64-linux-gnu libc6-dev-arm64-cross
+              apt-get install -y gcc-aarch64-linux-gnu libc6-dev-arm64-cross lld
+              # The napi-rs docker image pre-sets CC_aarch64_unknown_linux_gnu and
+              # CFLAGS pointing to its custom cross-toolchain at
+              # /usr/aarch64-unknown-linux-gnu, whose sysroot lacks stdatomic.h.
+              # Unset and switch to the Debian cross-toolchain so aws-lc-sys
+              # can find C11 atomics.
+              unset CFLAGS
+              unset CC_aarch64_unknown_linux_gnu
+              unset CXX_aarch64_unknown_linux_gnu
+              unset AR_aarch64_unknown_linux_gnu
               export CC_aarch64_unknown_linux_gnu=aarch64-linux-gnu-gcc
               export CXX_aarch64_unknown_linux_gnu=aarch64-linux-gnu-g++
               export AR_aarch64_unknown_linux_gnu=aarch64-linux-gnu-ar