Make all linker warnings errors in CI

Give us a better chance of detecting any kind of link issues or
user-visible warnings in advance.

Author: tgross35

ci/run.sh

@@ -19,6 +19,15 @@ if [ "${USING_CONTAINER_RUSTC:-}" = 1 ]; then
         rustup target add "$target"
 fi
 
+# Make all linker warnings errors
+if [[ "$target" == *"-apple-"* || "$target" == "thumb"* ]]; then
+    extra_rustflags=""
+else
+    extra_rustflags=" -Clink-arg=-Wl,--fatal-warnings"
+fi
+
+export RUSTFLAGS="${RUSTFLAGS:-}$extra_rustflags"
+
 # Test our implementation
 if [ "${NO_STD:-}" = "1" ]; then
     echo "nothing to do for no_std"