Sorry, I'm a little confused by your mail.

1. What platform are you building on?
2. What is 'make' on said platform?

If for instance its NetBSD and 'make' is netbsd's make, then 
you may simply need a newer version of bmake.  If the one in 
-current pkgsrc/devel/bmake doesn't work for you - then that's a bug.
bmake should be almost exactly equivalent to -current netbsd make.

If however 'make' means GNU make, then its a bit more interesting.
If the IMakefile contains stuff that relies on gmake behavior, then the 
package should have a dependency on gmake.

In general though I'd expect that a hardcoded 'make' in these cases 
will be wrong far more often than it is right.
Which is probably why it was switched to @MAKE@.

> RCS file: /cvsroot/pkgsrc/pkgtools/xpkgwedge/files/pkgxmkmf.in,v
> -    make Makefiles &&
> +    @MAKE@ Makefiles &&

>doesn't work for some packages where ${MAKE} is bmake.

> ===> Buildlinking for xpm-3.4knb1
> ===> Configuring for xpm-3.4knb1
> imake -DUseInstalled -I/home/jonp/pkg/lib/X11/config -I/usr/openwin/lib/X11/config
> make Makefiles
> bmake: "/home/jonp/src/pkgsrc/graphics/xpm/work/xpm-3.4k/Makefile" line 295: Unassociated shell command "SERVERMODULES = /usr/openwin/server/modules"

Sounds like there is white-space at the start of an assignment?

--sjg