[compiler-rt][asan][win] Intercept exceptions for i686 MinGW

[alvinhochun]

Summary

The i686-w64-windows-gnu target does not use SEH (which MSVC uses),
but DWARF-2 exception handling or possibly sjlj depending on the
toolchain build options. On this target we have to actually intercept
functions in libc++ and libunwind which handles throwing exceptions.
This fixes the TestCases/intercept-rethrow-exception.cpp test.

The x86_64-w64-windows-gnu target already works because it uses SEH
which is handled by intercepting RaiseException, so this change does not
affect x86_64.

Depends on D148990

[mstorsjo]

LGTM, thanks!

compiler-rt/lib/asan/asan_interceptors.h

 #endif
 
 #if SANITIZER_GLIBC
 # define ASAN_INTERCEPT___LONGJMP_CHK 1
 #else
 # define ASAN_INTERCEPT___LONGJMP_CHK 0
 #endif
 
-#if ASAN_HAS_EXCEPTIONS && !SANITIZER_WINDOWS && !SANITIZER_SOLARIS && \
-    !SANITIZER_NETBSD
+#if ASAN_HAS_EXCEPTIONS && !SANITIZER_SOLARIS && !SANITIZER_NETBSD && \
+    (!SANITIZER_WINDOWS || (defined(__MINGW32__) && defined(__i386__)))
 # define ASAN_INTERCEPT___CXA_THROW 1
 # define ASAN_INTERCEPT___CXA_RETHROW_PRIMARY_EXCEPTION 1
 # if defined(_GLIBCXX_SJLJ_EXCEPTIONS) || (SANITIZER_IOS && defined(__arm__))
 #  define ASAN_INTERCEPT__UNWIND_SJLJ_RAISEEXCEPTION 1
 # else
 #  define ASAN_INTERCEPT__UNWIND_RAISEEXCEPTION 1
 # endif
 #else

compiler-rt/lib/interception/interception_win.cpp

 static void **InterestingDLLsAvailable() {
   static const char *InterestingDLLs[] = {
       "kernel32.dll",
       "msvcr100.dll",      // VS2010
       "msvcr110.dll",      // VS2012
       "msvcr120.dll",      // VS2013
       "vcruntime140.dll",  // VS2015
       "ucrtbase.dll",      // Universal CRT
+#if (defined(__MINGW32__) && defined(__i386__))
+      "libc++.dll",        // libc++
+      "libunwind.dll",     // libunwind
+#endif
       // NTDLL should go last as it exports some functions that we should
       // override in the CRT [presumably only used internally].
       "ntdll.dll", NULL};
   static void *result[ARRAY_SIZE(InterestingDLLs)] = { 0 };
   if (!result[0]) {
     for (size_t i = 0, j = 0; InterestingDLLs[i]; ++i) {
       if (HMODULE h = GetModuleHandleA(InterestingDLLs[i]))
         result[j++] = (void *)h;