Fix WindowsDebugLogger hang on release builds

Removes ASSERT checking the status of the exit
handle so it cannot ever be optimized out.

BUG=dawn:592

Change-Id: Ib88a058abd0597668ba3c272cf0e304f4aa19c4e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/34761
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/utils/WindowsDebugLogger.cpp

@@ -89,7 +89,8 @@ namespace utils {
             }
 
             if (mShouldExitHandle != nullptr) {
-                ASSERT(SetEvent(mShouldExitHandle) != 0);
+                BOOL result = SetEvent(mShouldExitHandle);
+                ASSERT(result != 0);
                 CloseHandle(mShouldExitHandle);
             }