fix build on Cygwin

llvm-svn: 297378
diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index 568b1b4..43549c0 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -372,6 +372,9 @@
   default:
     return true;
   }
+#elif defined(__CYGWIN__)
+  // Cygwin doesn't expose this information; would need to use Win32 API.
+  return false;
 #else
   return !!(STATVFS_F_FLAG(Vfs) & MNT_LOCAL);
 #endif