__has_attribute error compiling PictureFrame

[mickbert]

Hello.
I have just downloaded gap from github [1], and I am trying to compile 
them on a RHEL 7, with gcc 4.8.5 20150623 (Red Hat 4.8.5-36)

When I arrive to PictureFrame, compiling the source 
PreferencesController.m, I got the trange error:

In file included from /usr/local/include/Foundation/NSObject.h:30:0,
                 from 
/usr/local/include/Foundation/FoundationErrors.h:29,
                 from /usr/local/include/Foundation/Foundation.h:33,
                 from /usr/local/include/Cocoa/Cocoa.h:33,
                 from PreferencesController.h:5,
                 from PreferencesController.m:6:
/usr/local/include/Foundation/NSObjCRuntime.h:187:20: error: missing 
binary operator before token "("
 #if __has_attribute(objc_designated_initializer)

"Strange" because it looks to be in a deep foundation header, and I have 
compiled quite a lot of program before, without any issue. Is it 
possible that header has never been included anywhere?

Any suggestion?

[1] https://github.com/gnustep/gap
--
Mick