sanitizer_common: allow COMMON_INTERCEPTOR_ENTER to use labels

[dvyukov]

Summary

The memcpy interceptor is the only one that uses COMMON_INTERCEPTOR_ENTER
more than once in a single function. This does not allow COMMON_INTERCEPTOR_ENTER
to use labels, because they are global for the whole function (not block scoped).
Don't include COMMON_INTERCEPTOR_ENTER code twice.

compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc

 #define wait4 __wait450
 extern const unsigned short *_ctype_tab_;
 extern const short *_toupper_tab_;
 extern const short *_tolower_tab_;
 #endif
 
 // Platform-specific options.
 #if SANITIZER_MAC
-#define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE false
+#define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE 0
 #elif SANITIZER_WINDOWS64
-#define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE false
+#define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE 0
 #else
-#define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE true
+#define PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE 1
 #endif  // SANITIZER_MAC
 
 #ifndef COMMON_INTERCEPTOR_INITIALIZE_RANGE
 #define COMMON_INTERCEPTOR_INITIALIZE_RANGE(p, size) {}
 #endif
 
 #ifndef COMMON_INTERCEPTOR_UNPOISON_PARAM
 #define COMMON_INTERCEPTOR_UNPOISON_PARAM(count) {}

 #if SANITIZER_INTERCEPT_MEMCPY
 INTERCEPTOR(void *, memcpy, void *dst, const void *src, uptr size) {
   // On OS X, calling internal_memcpy here will cause memory corruptions,
   // because memcpy and memmove are actually aliases of the same
   // implementation.  We need to use internal_memmove here.
   // N.B.: If we switch this to internal_ we'll have to use internal_memmove
   // due to memcpy being an alias of memmove on OS X.
   void *ctx;
-  if (PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE) {
+#if PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE
     COMMON_INTERCEPTOR_MEMCPY_IMPL(ctx, dst, src, size);
-  } else {
+#else
     COMMON_INTERCEPTOR_MEMMOVE_IMPL(ctx, dst, src, size);
-  }
+#endif
 }
 
 #define INIT_MEMCPY                                  \
   do {                                               \
     if (PLATFORM_HAS_DIFFERENT_MEMCPY_AND_MEMMOVE) { \
       COMMON_INTERCEPT_FUNCTION(memcpy);             \
     } else {                                         \
       ASSIGN_REAL(memcpy, memmove);                  \