What is a DRF file? Why is there a problem creating it?

Problem/Question/Abstract:

I just ran in a problem rebuilding the latest version of the TMultiLang package.
This is done by a batch file which invokes the command line compiler DCC32.EXE
I got this error message:

E:\Projects\MultiLang\mle>dcc32 multilang.dpk
Delphi for Win32 Version 10.0 Copyright (c) 1983,97 Borland International
MultiLang.dpk(40) Fatal: Could not create output file 'MultiLang.drf'

What is this DRF file? Why did I get this message?

Answer:

When you compile with packages, you can specify which packages should be considered for linkage. The package requirements of the project get stored into a temporary Windows resource file with a .DRF extension.

In my case I got this error message from DCC32 because my environment variable %TEMP% pointed to an not existing directory after I had cleaned up too much :-)