[Support] Fix lifetime of file descriptors when using MemoryBuffer.

Clients of MemoryBuffer::getOpenFile expect it not to take ownership of the file
descriptor passed in. So don't.

llvm-svn: 176995

llvm/lib/Support/FileOutputBuffer.cpp

@@ -70,8 +70,8 @@ error_code FileOutputBuffer::create(StringRef FilePath,
   if (EC)
     return EC;
 
-  OwningPtr<mapped_file_region> MappedFile(
-    new mapped_file_region(FD, mapped_file_region::readwrite, Size, 0, EC));
+  OwningPtr<mapped_file_region> MappedFile(new mapped_file_region(
+      FD, true, mapped_file_region::readwrite, Size, 0, EC));
   if (EC)
     return EC;