> From: rillig@NetBSD.org
> 
> The toolchain utilities like ar, as, ld, strip, size should be
> integrated into the tools framework. This makes it possible to install
> binutils on Solaris and keep pkgsrc working.
> 
> Currently, the GNU binutils are not supported on Solaris by pkgsrc, and
> indeed they do not work. But if they are installed and ${LOCALBASE}/bin
> is before /usr/ccs/bin in the path, most packages will use them instead
> of the native ones, leading to build failure.
> 

And what about a kind of second stage of boostrap for all tools
 needed by Solaris.
maybe a meta-pkg or somethings like xpkgwedge or x11-links

And tools.SunOS.mk could be write like:

...
.if exists(/usr/pkg/bin/ggrep)
TOOLS_PLATFORM.egrep?=          /usr/pkg/bin/gegrep
TOOLS_PLATFORM.fgrep?=          /usr/pkg/bin/gfgrep
TOOLS_PLATFORM.grep?=           /usr/pkg/bin/ggrep
.endif
TOOLS_PLATFORM.egrep?=          /usr/xpg4/bin/grep -E
TOOLS_PLATFORM.fgrep?=          /usr/xpg4/bin/fgrep
TOOLS_PLATFORM.grep?=           /usr/xpg4/bin/grep
...

Just an idea.
Gilles