Fix a bug in my previous change to this, which broke the build on sparcs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20184 91177308-0d34-0410-b5e6-96231b3b80d8

lib/System/Unix/Unix.h

@@ -77,7 +77,7 @@ inline void ThrowErrno(const std::string& prefix) {
     // Copy the thread un-safe result of strerror into
     // the buffer as fast as possible to minimize impact
     // of collision of strerror in multiple threads.
-    if (Errno)
+    if (errno)
       strncpy(buffer,strerror(errno),MAXPATHLEN-1);
     buffer[MAXPATHLEN-1] = 0;
 #else