[CMake] target_include_directories SYSTEM adds -isystem to Clang, but not GCC

[Gregor Jasny]

Hello,

On 17/08/15 01:01, digitalriptide wrote:
> When I add SYSTEM to target_include_directories, for example using
> target_include_directories( my_target SYSTEM PUBLIC ${MY_LIBRARIES} )
> in Clang, CMake prepends -isystem to the relavent -I/my/library/path
> type flags. With GCC, however, I see no -isystem added.
>
> For reference, this is CMake 3.2.3 on OS X with Apple LLVM version 6.0
> and GCC 5 provided via MacPorts.
>
> Should SYSTEM add -isystem with GCC?

this is a know bug: http://www.cmake.org/Bug/view.php?id=15687

I plan to work on it during the next days so that it may be fixed with 
CMake 3.4.

Thanks,
Gregor