Fix typo from r362990 to fix Windows builds

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@362997 91177308-0d34-0410-b5e6-96231b3b80d8

Author: tstellar

include/llvm/Support/Compiler.h

@@ -110,7 +110,7 @@
 #define LLVM_EXTERNAL_VISIBILITY __attribute__ ((visibility("default")))
 #else
 #define LLVM_LIBRARY_VISIBILITY
-#define LLVM_EXTERNAL_VISIBLITY
+#define LLVM_EXTERNAL_VISIBILITY
 #endif
 
 #if defined(__GNUC__)