hasDisassembler should return false if disassembler isn't available.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58682 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/System/Disassembler.cpp b/lib/System/Disassembler.cpp
index f44dd7f..378fe26 100644
--- a/lib/System/Disassembler.cpp
+++ b/lib/System/Disassembler.cpp
@@ -30,10 +30,14 @@
 {
 #if defined (__i386__) || defined (__amd64__) || defined (__x86_64__)
   // We have option to enable udis86 library.
+# if USE_UDIS86
   return true;
 #else
   return false;
 #endif
+#else
+  return false;
+#endif
 }
 
 std::string llvm::sys::disassembleBuffer(uint8_t* start, size_t length,