clang builds and /var/tmp

[Richard PALO <richard%netbsd.org@localhost>]

just noticed with concern with clang that /var/tmp is used by default during builds.

I have WRKOBJDIR set to /tmp/pkgsrc and no where else do I stipulate TMP or TMPDIR

In any event, never to /var/tmp

> richard@omnis:/tmp/pkgsrc/lang/clang/work$ grep var\/tmp */*
> build/config.log:setupterm                           /var/tmp//cc_rqEmo.o
> build/config.log:el_init                             /var/tmp//cc7zWSmo.o
> build/config.log:mallinfo                            /var/tmp//ccjEWZmo.o
> build/config.log:__crashreporter_info__              /var/tmp//cc8_WJpo.o
> build/config.log:strtoq                              /var/tmp//ccoiG.ro.o
> build/config.log:malloc_zone_statistics              /var/tmp//ccTnGmso.o
> build/config.log:futimes                             /var/tmp//cceEq6so.o

the only thing I specifically notice setting this is in getDefaultTempDir():
> richard@omnis:/tmp/pkgsrc/lang/clang/work$ grep var\/tmp */*/*/*/*
> llvm-3.7.0.src/include/llvm/Support/Path.h:/// "/var/tmp" or "C:/TEMP"
> llvm-3.7.0.src/lib/Support/Unix/Path.inc:  return "/var/tmp";
but can't seem to find any callers..

Is there somewhere else this can identified?  I find nothing in pkgsrc/mk setting /var/tmp to TMP or TMPDIR excepting the following, apparently not relevant here:
>bsd.pkg.readme.mk:              TMPDIR=${TMPDIR:U/tmp:Q} \

Anybody else suffer this?

This seems to be killing my boot SSD which is supposed to be, for the most part, read-only. I have my swap on a different fast SSD + 32G ram.

If I `bmake configure TMPDIR=/tmp' it seems to do the right thing... for my environment
setting TMPDIR=${WKROBJDIR}/tmp seems reasonable, but does that mean I need to add it to ALL_ENV myself in etc/mk.conf.

What is the correct procedure?

-- 
Richard PALO