Add Rust AddressSanitizer CI coverage

Run the Rust usage test suite under AddressSanitizer on Linux.

This adds continuous sanitizer coverage for FlatBuffers' Rust code and
helps detect memory-safety regressions in unsafe code paths.

The configuration was validated locally on x86_64 Linux with nightly
Rust and rust-src, with the complete Rust usage test suite passing
under AddressSanitizer.

Refs #6401.

Author: fredlday-oss

.github/workflows/build.yml

@@ -444,6 +444,23 @@ jobs:
       working-directory: tests
       run: bash RustTest.sh
 
+  build-rust-linux-asan:
+    name: Build Rust Linux ASan
+    runs-on: ubuntu-24.04
+    steps:
+    - uses: actions/checkout@v6
+    - name: Install nightly Rust with rust-src
+      run: rustup toolchain install nightly --profile minimal --component rust-src
+    - name: Test Rust with AddressSanitizer
+      env:
+        RUSTFLAGS: -Zsanitizer=address
+        RUSTDOCFLAGS: -Zsanitizer=address
+      run: |
+        cargo +nightly test \
+          -Zbuild-std \
+          --target x86_64-unknown-linux-gnu \
+          --manifest-path tests/rust_usage_test/Cargo.toml
+
   build-rust-windows:
     name: Build Rust Windows
     runs-on: windows-2022