Introspection build issue with graphene

We're seeing this on i686 in the RHEL buildsystem:

<mock-chroot> sh-5.0# ninja -C build
ninja: Entering directory `build'
[1/2] Generating Graphene-1.0.gir with a custom command
gcc -pthread -E -D_GNU_SOURCE -DGRAPHENE_COMPILATION -I. -I/builddir/build/BUILD/graphene-1.10.4/build/include -I/builddir/build/BUILD/graphene-1.10.4/include -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/gobject-introspection-1.0 -I/builddir/build/BUILD/graphene-1.10.4/src -I/builddir/build/BUILD/graphene-1.10.4/build/src -o g-ir-cpp-w81vx1kk.i -C /builddir/build/BUILD/graphene-1.10.4/build/g-ir-cpp-w81vx1kk.c
/usr/lib/gcc/i686-redhat-linux/10/include/stddef.h:424: syntax error, unexpected identifier in '  __float128 __max_align_f128 __attribute__((__aligned__(__alignof(__float128))));' at '__float128'
gcc -pthread -D_GNU_SOURCE -I/builddir/build/BUILD/graphene-1.10.4/src -I/builddir/build/BUILD/graphene-1.10.4/build/src -I/builddir/build/BUILD/graphene-1.10.4/build/include -I/builddir/build/BUILD/graphene-1.10.4/include -I/builddir/build/BUILD/graphene-1.10.4/build/include -I/builddir/build/BUILD/graphene-1.10.4/include -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/libmount -I/usr/include/blkid -I/builddir/build/BUILD/graphene-1.10.4/build/include -I/builddir/build/BUILD/graphene-1.10.4/include -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/gobject-introspection-1.0 -c /builddir/build/BUILD/graphene-1.10.4/build/tmp-introspectc67xtc2g/Graphene-1.0.c -o /builddir/build/BUILD/graphene-1.10.4/build/tmp-introspectc67xtc2g/Graphene-1.0.o -Wno-deprecated-declarations -pthread
g-ir-scanner: link: gcc -pthread -o /builddir/build/BUILD/graphene-1.10.4/build/tmp-introspectc67xtc2g/Graphene-1.0 /builddir/build/BUILD/graphene-1.10.4/build/tmp-introspectc67xtc2g/Graphene-1.0.o -L. -Wl,-rpath,. -Wl,--no-as-needed -L/builddir/build/BUILD/graphene-1.10.4/build/src -Wl,-rpath,/builddir/build/BUILD/graphene-1.10.4/build/src -lgraphene-1.0 -lm -lgobject-2.0 -lglib-2.0 -lgirepository-1.0 -lgio-2.0 -lgobject-2.0 -Wl,--export-dynamic -lgmodule-2.0 -pthread -lglib-2.0 -lglib-2.0
[2/2] Generating Graphene-1.0.typelib with a custom command

Looking a bit closer, this is because stddef.h contains:

  /* _Float128 is defined as a basic type, so max_align_t must be
     sufficiently aligned for it.  This code must work in C++, so we
     use __float128 here; that is only available on some
     architectures, but only on i386 is extra alignment needed for
     __float128.  */
#ifdef __i386__
  __float128 __max_align_f128 __attribute__((__aligned__(__alignof(__float128))));
#endif

So, maybe this (untested) patch would do?

diff --git a/giscanner/scannerlexer.l b/giscanner/scannerlexer.l
index cfec4d58..8b3ecfe2 100644
--- a/giscanner/scannerlexer.l
+++ b/giscanner/scannerlexer.l
@@ -217,6 +217,8 @@ stringtext                          ([^\\\"])|(\\.)
 "enum"                                 { return ENUM; }
 "extern"                               { return EXTERN; }
 "float"                                        { return BASIC_TYPE; }
+"__float80"                            { return BASIC_TYPE; }
+"__float128"                           { return BASIC_TYPE; }
 "_Float16"                              { return BASIC_TYPE; }
 "_Float32"                              { return BASIC_TYPE; }
 "_Float64"                              { return BASIC_TYPE; }