xorgproto fallout NetBSD 7.1-STABLE in pkgcomp chroot

[Mike Pumford <mpumford%mudcovered.org.uk@localhost>]

I'm trying to build packages with X11_TYPE=native on 7.1 stable but I 
keep running into situations where it goes off and installs the modular 
X11 libraries and components from pkgsrc.

I do my builds in a pkg_comp1 chroot on an 8.0-BETA system using libkver 
so I suspect something about that setup is causing trouble. Looking at 
the x11-links build output I see:

 PKG_COMP ==> Building and installing pkgtools/x11-links
make[1]: "../../mk/buildlink3/../../mk/buildlink3/pkgconfig-builtin.mk" 
line 55: warning: Couldn't read shell's output for "/usr/bin/sed -n -e 
's/Version: 7\.0\.31/2018.1/p'  /usr/X11R7/lib/pkgconfig/xproto.pc"
make: "../../mk/buildlink3/../../mk/buildlink3/pkgconfig-builtin.mk" 
line 55: warning: Couldn't read shell's output for "/usr/bin/sed -n -e 
's/Version: 7\.0\.31/2018.1/p'  /usr/X11R7/lib/pkgconfig/xproto.pc"

7.0.31 is the xproto version for the 8.0-BETA system but the X sets in 
the chroot have version 7.0.26 (which is why the sed command fails).

I did try and puzzle my way through pkgconfig-builtin.mk but I couldn't 
figure out where it was picking up the version numver to use on the left 
hand side of the sed substitution. Happy to dig further is someone can 
give me a few clues as to how I can trace or debug what is going on a 
bit further.

Mike