toolchain/44459: build.sh fails to build when /tmp is mounted noexec

[Pierre Pronchery <khorben%defora.org@localhost>]

>Number:         44459
>Category:       toolchain
>Synopsis:       build.sh fails to build when /tmp is mounted noexec
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jan 25 15:55:00 +0000 2011
>Originator:     Pierre Pronchery
>Release:        NetBSD 5.1_STABLE
>Organization:
>Environment:
System: NetBSD kwarx.defora.lan 5.1_STABLE NetBSD 5.1_STABLE (GENERIC) #0: Mon 
Jan 24 15:02:10 CET 2011 
khorben%kwarx.defora.lan@localhost:/home/amd64/obj/sys/arch/amd64/compile/GENERIC
 amd64
Architecture: x86_64
Machine: amd64
>Description:
On my system, /tmp is a mfs mounted with the "noexec" flag.
Unfortunately, this seems to break proper operation of the build.sh
script.

>How-To-Repeat:
# mount -t mfs -o noexec mfs /tmp
# cd /usr/src
# ./build.sh tools
[...]
checking whether the C compiler works... configure: error: cannot run C
compiled programs.
If you meant to cross compile, use `--host'.

ERROR: Configure of nbmake failed
*** BUILD ABORTED ***

>Fix:
Forcing TMPDIR to be a different location, with execution permissions,
bypasses the issue:
# TMPDIR=$HOME ./build.sh tools
[...]
checking whether the C compiler works... yes
checking whether we are cross compiling... no

A suggestion on IRC was to default to OBJDIR instead, and supply it as
TMPDIR within the environment during compilation. I think this would
make sense indeed.