Description of problem:
When both 32 and 64 versions of the glib2-devel package are installed, the anaconda package fails to be rebuilt:

# rpmbuild --rebuild ./anaconda-13.21.249-1.el6.src.rpm
...
Making all in isys
make[2]: Entering directory `/root/rpmbuild/BUILD/anaconda-13.21.249/isys'
  CC     libisys_la-devices.lo
  CC     libisys_la-imount.lo
  CC     libisys_la-cpio.lo
  CC     libisys_la-uncpio.lo
  CC     libisys_la-dasd.lo
  CC     libisys_la-lang.lo
  CC     libisys_la-isofs.lo
  CC     libisys_la-linkdetect.lo
  CC     libisys_la-vio.lo
  CC     libisys_la-ethtool.lo
  CC     libisys_la-eddsupport.lo
  CC     libisys_la-iface.lo
In file included from /usr/include/glib-2.0/glib/gasyncqueue.h:34,
                 from /usr/include/glib-2.0/glib.h:34,
                 from iface.c:46:
/usr/include/glib-2.0/glib/gthread.h: In function 'g_once_init_enter':
/usr/include/glib-2.0/glib/gthread.h:347: error: size of array 'type name' is negative
make[2]: *** [libisys_la-iface.lo] Error 1
make[2]: Leaving directory `/root/rpmbuild/BUILD/anaconda-13.21.249/isys'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/root/rpmbuild/BUILD/anaconda-13.21.249'
make: *** [all] Error 2
error: Bad exit status from /var/tmp/rpm-tmp.APQpFM (%build)

Version-Release number of selected component (if applicable):
anaconda-13.21.249-1.el6
glib2-devel-2.28.8-5.el6

How reproducible:
always

Steps to Reproduce:
1. install all dependencies required to rebuild anaconda
2. install glib2-devel.i686
3. rpmbuild --rebuild ./anaconda-13.21.249-1.el6.src.rpm

Actual results:
rebuild fails

Expected results:
rebuild finishes successfully