[compiler-rt][asan|win] Fix ASAN exception handler missing import

[etienneb]

Summary

This patch is adding a missing ASAN API redirection from an instrumented DLL.
The bug was introduced here:

https://reviews.llvm.org/D29463

This is causing this chromium bug:

https://bugs.chromium.org/p/chromium/issues/detail?id=692580

[rnk]

Looks good. I guess I forgot to add a test for this API.

[etienneb]

fix linux unittests

[rnk]

Looks good

lib/asan/asan_win_dll_thunk.cc

INTERCEPTOR(int, _except_handler4, void *a, void *b, void *c, void *d) {
   __asan_handle_no_return();
   return REAL(_except_handler4)(a, b, c, d);
 }
 #endif
 
 // Window specific functions not included in asan_interface.inc.
 INTERCEPT_WRAP_W_V(__asan_should_detect_stack_use_after_return)
 INTERCEPT_WRAP_W_V(__asan_get_shadow_memory_dynamic_address)
+INTERCEPT_WRAP_W_W(__asan_unhandled_exception_filter)
 
 using namespace __sanitizer;
 
 extern "C" {
 int __asan_option_detect_stack_use_after_return;
 uptr __asan_shadow_memory_dynamic_address;
 } // extern "C"