[Bug 1427000] New: c2hs does not like gcc7 __float128

https://bugzilla.redhat.com/show_bug.cgi?id=1427000

Bug ID: 1427000
           Summary: c2hs does not like gcc7 __float128
           Product: Fedora
           Version: rawhide
         Component: gtk2hs-buildtools
          Assignee: [e-mail]
          Reporter: [e-mail]
        QA Contact: [e-mail]
                CC: [e-mail],
                    [e-mail]

Description of problem:
gtk2hs packages are failing to build on i686 in F26 Rawhide with gcc7
due to the addition of a __float128 alignment directive in stddef.h.

Configuring glib-0.13.2.2...
+ '[' -x Setup ']'
+ LANG=en_US.utf8
+ ./Setup build
Building glib-0.13.2.2...
Preprocessing library glib-0.13.2.2...
gtk2hsC2hs: Error in C header file.
/usr/lib/gcc/i686-redhat-linux/7/include/stddef.h:435: (column 3) [FATAL]
> > > Syntax error!

The symbol `__float128' does not fit here.

Version-Release number of selected component (if applicable):
gtk2hs-buildtools-0.13.2.2
gcc-7.0.1-0.10.fc26

How reproducible:
100%

Steps to Reproduce:
1. try to build ghc-glib, ghc-gio, ghc-pango, ghc-gtk3, etc

Actual results:
see above

Expected results:
no failure

Additional info:
Upstream report https://github.com/gtk2hs/gtk2hs/issues/200