fuzzing: When fuzzing, always ASSERT, and abort() instead of SIGTRAP

Currently, when we hit an assertion failure, the fuzzer stops
immediately without producing a crash. This patch makes it so that we do
a hard abort instead which will be caught.

Bug: dawn:295, dawn:293
Fixes: dawn:293
Change-Id: Ie00074e84b51c9aa364aba96c11a35659bbba740
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/14682
Commit-Queue: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/common/Assert.cpp

@@ -15,11 +15,17 @@
 #include "common/Assert.h"
 #include "common/Log.h"
 
+#include <cstdlib>
+
 void HandleAssertionFailure(const char* file,
                             const char* function,
                             int line,
                             const char* condition) {
     dawn::ErrorLog() << "Assertion failure at " << file << ":" << line << " (" << function
                      << "): " << condition;
+#if defined(DAWN_ABORT_ON_ASSERT)
+    abort();
+#else
     DAWN_BREAKPOINT();
+#endif
 }