Pin nightly version for sanitizer tests

Author: a1phyr

.github/workflows/ci.yml

@@ -196,7 +196,9 @@ jobs:
         sanitizer: [address, leak, memory, thread]
     steps:
     - uses: actions/checkout@v4
-    - uses: dtolnay/rust-toolchain@nightly
+    # FIXME: revert to using the latest nightly when https://github.com/rust-lang/rust/issues/146465 is fixed.
+    - uses: dtolnay/rust-toolchain@master
+      toolchain: nightly-2025-09-05
     - name: Add rust source
       run: rustup component add rust-src
     - name: Run tests with sanitizer