[dart2wasm] Fix compile_benchmark script with stress test mode.

Fixes 'web/wasm/flute_stress_test' failure seen at https://dart-ci.firebaseapp.com/#10be4da5dc9dadb22b9c25a6174fff436e8b63e2

Change-Id: I64b2097f9059b80ec72c268e2105a88f0f4e40bd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/453620
Reviewed-by: Mayank Patke <[email protected]>
Commit-Queue: Nate Biggs <[email protected]>

Author: natebiggs

pkg/dart2wasm/tool/compile_benchmark

@@ -151,9 +151,9 @@ while [ $# -gt 0 ]; do
       shift
       ;;
 
-    --extra-compiler-option=--enable-multi-module-stress-test)
+    --extra-compiler-option=--enable-multi-module-stress-test-mode)
       MULTI_MODULE=1
-      DART2WASM_ARGS+=("--enable-multi-module-stress-test")
+      DART2WASM_ARGS+=("--enable-multi-module-stress-test-mode")
       shift
       ;;