#1. Since the syntax is not the same for the different command line tools, I thought it was a mistake.
#2. The POIDE project files have this syntax, so I thought the response-file syntax would also. I guess not.
#3. It seems that CC only has the /x option to block looking in the path defined in the registry. You still have to set the include paths individually for POCC and POLINK.
I had some trouble figuring out the option syntax for CC, because the docs are not clear. With POCC and POLINK, you have to write
pocc -I Include file.c
polink -libpath:Lib file.obj
but this does not work with CC
cc -x -I Include file.c -libpath:Lib file.obj
Instead, you always have to put quotes for the POCC path option, like this
cc -x -I"Include" file.c -libpath:Lib file.obj