[UBSan] Explicitly list all supported OS/arch pairs supported by UBSan.

llvm-svn: 233295
diff --git a/compiler-rt/lib/ubsan/ubsan_init.cc b/compiler-rt/lib/ubsan/ubsan_init.cc
index 219273d..9527269 100644
--- a/compiler-rt/lib/ubsan/ubsan_init.cc
+++ b/compiler-rt/lib/ubsan/ubsan_init.cc
@@ -11,6 +11,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "ubsan_platform.h"
+#if CAN_SANITIZE_UB
 #include "ubsan_diag.h"
 #include "ubsan_init.h"
 #include "ubsan_flags.h"
@@ -61,3 +63,5 @@
 };
 static UbsanInitializer ubsan_initializer;
 #endif  // SANITIZER_CAN_USE_PREINIT_ARRAY
+
+#endif  // CAN_SANITIZE_UB