toolchain/56726: clang can't build llvm with MKDEBUG=yes

[martin%NetBSD.org@localhost]

>Number:         56726
>Category:       toolchain
>Synopsis:       clang can't build llvm with MKDEBUG=yes
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Feb 21 14:30:00 +0000 2022
>Originator:     Martin Husemann
>Release:        NetBSD 9.99.93
>Organization:
Thet NetBSD Foundation, Inc.
>Environment:
System: NetBSD martins.aprisoft.de 9.99.93 NetBSD 9.99.93 (GENERIC) #94: Wed Dec 29 13:22:36 CET 2021 martin%martins.aprisoft.de@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:

The amd64 and the aarch64 LLVM builds are failing on the build cluster due
to some unknown issue and MKDEBUG=yes.

It is unlikely they run into any kind of space issues, unless clang does
not obey TMPDIR. The exact reason is not clear, it seems to be a dying
linker invocation of some kind.

Using MKDEBUG=no makes the build work.

>How-To-Repeat:

Not sure - the exact command lines of the last failed runs were:

build.sh -m evbarm -a aarch64 -B 202202202140Z -V NETBSD_OFFICIAL_RELEASE=no -D /home/builds/ab/HEAD-llvm/evbarm-aarch64/202202202140Z-dest -M /home/builds/ab/HEAD-llvm/evbarm-aarch64/202202202140Z-obj -R /home/builds/ab/HEAD-llvm/evbarm-aarch64/202202202140Z-rlse -T /home/builds/ab/HEAD-llvm/evbarm-aarch64/202202202140Z-tools -U -X /home/source/ab/HEAD-llvm/xsrc -x -N0 -V TMPDIR=/tmp -V BUILD=yes -V MKLLVM=yes -V HAVE_LLVM=yes -V MKGCC=no -V MAKECONF=/home/builds/etc/make.conf -V MKDEBUG=yes -j16 release install-image iso-image
build.sh -m amd64 -B 202202202140Z -V NETBSD_OFFICIAL_RELEASE=no -D /home/builds/ab/HEAD-llvm/amd64/202202202140Z-dest -M /home/builds/ab/HEAD-llvm/amd64/202202202140Z-obj -R /home/builds/ab/HEAD-llvm/amd64/202202202140Z-rlse -T /home/builds/ab/HEAD-llvm/amd64/202202202140Z-tools -U -X /home/source/ab/HEAD-llvm/xsrc -x -N0 -V TMPDIR=/tmp -V BUILD=yes -V MKLLVM=yes -V HAVE_LLVM=yes -V MKGCC=no -V MAKECONF=/home/builds/etc/make.conf -V MKDEBUG=yes -j16 release iso-image install-image live-image

and /tmp is a tmpfs with 1.9G free space, while /var/tmp only has ~400 M free
space. The nbmake wrapper generated includes:

TMPDIR=/tmp; export TMPDIR

>Fix:
n/a