[compiler-rt] [asan] Use __SSE2__ (rather than __i686__...) for SSE2 test

[mgorny]

Summary

Use the SSE2 to determine whether SSE2 is enabled in the ASAN tests
rather than relying on either of the i686 and x86_64. The former
is only set with explicit -march=i686, and therefore misses most of
the x86 CPUs that support SSE2. SSE2 is in turn defined if
the current settings (-march, -msse2) indicate that SSE2 is supported
which should be more reliable.

[kcc]

LGTM,
assuming you have verified that the test is still executed.

[mgorny]

I did, even twice ;-). Thanks.

compiler-rt/trunk/lib/asan/tests/asan_test.cc

 TEST(AddressSanitizer, ThreadStackReuseTest) {
   pthread_t t;
   PTHREAD_CREATE(&t, 0, ThreadStackReuseFunc1, 0);
   PTHREAD_JOIN(t, 0);
   PTHREAD_CREATE(&t, 0, ThreadStackReuseFunc2, 0);
   PTHREAD_JOIN(t, 0);
 }
 
-#if defined(__i686__) || defined(__x86_64__)
+#if defined(__SSE2__)
 #include <emmintrin.h>
 TEST(AddressSanitizer, Store128Test) {
   char *a = Ident((char*)malloc(Ident(12)));
   char *p = a;
   if (((uintptr_t)a % 16) != 0)
     p = a + 8;
   assert(((uintptr_t)p % 16) == 0);
   __m128i value_wide = _mm_set1_epi16(0x1234);