[wasm][test] Fix for gcc 7.4

This fixes a compiler warning on gcc 7.4.

R=ahaas@chromium.org
CC=machenbach@chromium.org

Bug: v8:11716
Change-Id: I385765f1ac3de17eea1bb56109869636f8ae9d95
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2862779
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Auto-Submit: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74310}

test/unittests/wasm/trap-handler-x64-unittest.cc

@@ -246,7 +246,9 @@ class TrapHandlerTest : public TestWithIsolate,
         .Call();
     EXPECT_TRUE(g_test_handler_executed);
     g_test_handler_executed = false;
-    if (check_wasm_flag) EXPECT_FALSE(GetThreadInWasmFlag());
+    if (check_wasm_flag) {
+      EXPECT_FALSE(GetThreadInWasmFlag());
+    }
   }
 
   bool test_handler_executed() { return g_test_handler_executed; }