[CMake] Changing GCC_INPUT_TYPE for Mac

[Clemens Arth]

Hi,

is there a possibility to change the type of a file from a 
CMakeLists.txt file for Xcode? What I want to do is compiling a simple 
c++ file as objective-c++ instead of c++. As default mode, Xcode chooses 
the file extension to figure out what type the file is, but I want to 
avoid changing the extension of my file from cpp to mm. There is a 
switch in Xcode to change the default behaviour, but is there also a 
possibility to change it from cmake directly?

Regards
Clemens