Error trying to build Objective-C++ on Windows

[Doug Simons]

I'm getting a "No rule to make target" error when trying to compile some 
Objective-C++ files that I just added to my project on Windows. I haven't used 
Objective-C++ previously, so I googled around to find out what I need to do. I 
added a <product>_OBJCC_FILES section to list my .mm files, and also 
"CC=$(CXX)" but no luck.

Here's the relevant portion of my GNUmakefile:

CC=$(CXX)

APP_NAME=Eggplant

VERSION=__VERSION__

Eggplant_OBJCC_FILES=\
        ABBYYCommands.mm\
        NSString+Wchar.mm\
        Engine.mm

...

And here's the actual error:

make[4]: *** No rule to make target `obj/Eggplant.obj/ABBYYCommands.mm.o', 
needed by `Eggplant.app/./Eggplant.exe'.  Sto
p.
make[3]: *** [internal-app-run-compile-submake] Error 2
make[2]: *** [Eggplant.all.app.variables] Error 2
make[1]: *** [internal-all] Error 2
make: *** [internal-all] Error 2
_____________________________

Any clues about what I'm missing? Is there a compile flag I need to add 
somewhere? It looks as though it doesn't even recognize the .mm file type.

Thanks for any help!

Doug Simons