enable rustc debug assertions on -alt builds

just like llvm assertions

src/ci/run.sh

@@ -127,6 +127,13 @@ if [ "$DEPLOY$DEPLOY_ALT" = "1" ]; then
 
   CODEGEN_BACKENDS="${CODEGEN_BACKENDS:-llvm}"
   RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set rust.codegen-backends=$CODEGEN_BACKENDS"
+
+  # Unless explicitly disabled, we want rustc debug assertions on the -alt builds
+  if [ "$DEPLOY_ALT" != "" ]; then
+    if [ "$NO_DEBUG_ASSERTIONS" = "" ]; then
+      RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --enable-debug-assertions"
+    fi
+  fi
 else
   # We almost always want debug assertions enabled, but sometimes this takes too
   # long for too little benefit, so we just turn them off.