Allow explicit closing of the MappedFile, before destruction

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17759 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/System/MappedFile.h

@@ -121,6 +121,8 @@ namespace sys {
     /// @brief Set the size of the file and memory mapping.
     void size(size_t new_size);
 
+    void close() { terminate(); }
+
   /// @}
   /// @name Implementation
   /// @{