use __builtin_debugtrap() in sk_abort_no_print() where possible

I got a little jealous of the Windows version of this that breaks into
the debugger.  Using __builtin_debugtrap() here should have basically
the effect of abort() when not under a debugger, but lets you continue
on if you want when run under a debugger.

Change-Id: If5f12776758b1753ffad083b34a53661450b0812
Reviewed-on: https://skia-review.googlesource.com/156248
Auto-Submit: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>

src/ports/SkMemory_malloc.cpp

@@ -37,6 +37,8 @@ void sk_abort_no_print() {
 #endif
 #if defined(SK_DEBUG) && defined(SK_BUILD_FOR_WIN)
     __debugbreak();
+#elif defined(__clang__)
+    __builtin_debugtrap();
 #else
     abort();
 #endif