It is true, it happened to me also with version 3.1.0 of MinGW:
By default windres gives errors. It's nor enough to change -J to -I, I had to remove also the $res_includes option to eliminate the error message:
Directory : D:\Tutorial\mdi\
--------------------------------------------------------------------------------
Switching to target: default
Compiling: main.rc
windres.exe: unknown format type `C:\\MinGW\\include'
windres.exe: supported formats: rc res coff
Process terminated with status 1 (0 minutes, 0 seconds)
So with MinGW version 3.1.0-1 the functional line is:
$rescomp -i $file -I rc -o $resource_output -O coff
I did not tested this problem with the newer version of MinGW.