pkg/51074: devel/meld doesn't work with base Xorg

[coypu%sdf.org@localhost]

>Number:         51074
>Category:       pkg
>Synopsis:       devel/meld doesn't work with base Xorg
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Apr 18 04:40:00 +0000 2016
>Originator:     coypu
>Release:        pkgsrc-current, NetBSD-current
>Organization:
>Environment:
NetBSD net.Home 7.99.27 NetBSD 7.99.27 (GENERIC) #2: Thu Apr 14 12:13:00 IDT 2016  fly%net.Home@localhost:/usr/obj.amd64/sys/arch/amd64/compile/GENERIC amd64
>Description:
built devel/meld version 3.15.2 with unprivileged bootstrapped pkgsrc (I don't think this matters), with base Xorg.
it opens libGL.so, but looks in the wrong directory:

$ ktruss meld |grep libGL
Couldn't open libGL.so: Shared object "libGL.so" not found
   202      1 python2.7 open("/home/fly/pkg/lib/libGL.so", 0, 0x68) Err#2 ENOENT
   202      1 python2.7 open("/usr/lib/libGL.so", 0, 0x1) Err#2 ENOENT
       "Couldn't open libGL.so: Shared object "libGL.so" not found\n"

in my case, libGL.so is in /usr/X11R7/lib.

I believe this problem affects more than just this package, and exists for any python packages using libGL.so.
>How-To-Repeat:

>Fix:
tnn mentions that the fix should have:
-L${X11BASE}/lib ${COMPILER_RPATH_FLAG}${X11BASE}/lib

but I'm not sure where to put it.