Thank you very much. I actually didn't find a reference to gtk but searching for gui turned up a failure to find Intrinsic.h
Here is the part of the configure script responsible:
$as_echo_n "checking if X11 header files can be found... " >&6; }
cflags_save=$CFLAGS
CFLAGS="$CFLAGS $X_CFLAGS"
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <X11/Xlib.h>
#include <X11/Intrinsic.h>
int
main ()
{
;
return 0;
}
_ACEOF
The whole problem was a result of the way I installed my development support on CentOS, which was by installing the gtk3-devel package with yum (dnf). This installed the X development packages necessary for gtk, but it didn't install the (obsolescent) libXt-devel package. Installing that allowed a gui compilation. Perhaps this check in the configure script needs to be updated.
Anyway, I now have a working GUI vim!
Thanks again!