Rust: test that no heap allocs happen on hot paths (#5022)

tests/RustTest.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
-set -ex
+set -e
 #
 # Copyright 2018 Google Inc. All rights reserved.
 #
@@ -25,4 +25,13 @@ else
     exit 1
 fi
 
+cargo run --bin=alloc_check
+TEST_RESULT=$?
+if [[ $TEST_RESULT  == 0 ]]; then
+    echo "OK: Rust heap alloc test passed."
+else
+    echo "KO: Rust heap alloc test failed."
+    exit 1
+fi
+
 cargo bench