There was a function "export makefile" a long time ago, but it was sacked for being utterly broken and making more problems that it was good for.
There are currently no plans to reimplement this feature (although that does not mean we will never possibly do so).
If you can live with a makefile that has all its paths hardcoded, you can pretty much make your own makefile exporter rather easily, since you can query everything you need from the compiler plugin. The build process does not do things a lot differently, it asks for all files first, and then asks for a valid set of compiler options for each file.
If you get all files belonging to one target and get the compiler options for one of them, then you should only need to stream all of that to a text file, and you're done (more or less).
However, be warned that the compiler system is being worked over, so the API may change in the future.