Debug: Run tests with 1 single test thread

Author: qinsoon

.github/scripts/ci-test.sh

@@ -4,6 +4,9 @@ export RUST_BACKTRACE=1
 # Run all tests with 1G heap
 export MMTK_GC_TRIGGER=FixedHeapSize:1000000000
 
+# To debug
+export RUST_TEST_THREADS=1
+
 for_all_features "cargo test"
 
 # target-specific features