possible fix to "Parallel release failed on pwd_mkdb"

[op]

Summary

Possible solution to these build errors:

We got this build failure, when two concurrent make release running in parallel:

10-STABLE:

--------------------------------------------------------------
>>> stage 4.4: building everything
--------------------------------------------------------------
pwd_mkdb: /var/tmp/temproot/etc/pwd.db.tmp to
/var/tmp/temproot/etc/pwd.db: No such file or directory
*** Error code 1

Stop.
make[4]: stopped in /jenkins/workspace/HardenedBSD-10-STABLE-amd64/etc
*** Error code 1

Stop.
make[3]: stopped in /jenkins/workspace/HardenedBSD-10-STABLE-amd64
*** Error code 1

Stop.
make[2]: stopped in /jenkins/workspace/HardenedBSD-10-STABLE-amd64

  *** FATAL ERROR: Cannot 'cd' to
/jenkins/workspace/HardenedBSD-10-STABLE-amd64/release/.. and install
files to
      the temproot environment

*** Error code 1

Stop.
make[1]: stopped in /jenkins/workspace/HardenedBSD-10-STABLE-amd64/release
*** Error code 1

11-CURRENT:

pwd_mkdb -i -p -d /var/tmp/temproot/etc /var/tmp/temproot/etc/master.passwd
pwd_mkdb: /var/tmp/temproot/etc/pwd.db.tmp: File exists
*** Error code 1

Stop.
make[4]: stopped in /jenkins/workspace/HardenedBSD-master-amd64/etc
*** Error code 1

Stop.
make[3]: stopped in /jenkins/workspace/HardenedBSD-master-amd64
*** Error code 1

Stop.
make[2]: stopped in /jenkins/workspace/HardenedBSD-master-amd64

  *** FATAL ERROR: Cannot 'cd' to
/jenkins/workspace/HardenedBSD-master-amd64/release/.. and install
files to
      the temproot environment

*** Error code 1

Stop.
make[1]: stopped in /jenkins/workspace/HardenedBSD-master-amd64/release
*** Error code 1

Not yet tested.

[sjg]

It probably would have been sufficient to just do
TEMPROOT=/var/tmp/temproot$$

or

TEMPROOT=TMPDIR=/var/tmp mktemp -d -t temproot

and not otherwise fiddle with TMPDIR

[gjb]

Implementation question: What is the use case for running multiple 'release' targets in parallel?

[sjg]

In D3002#86258, @gjb wrote:

Implementation question: What is the use case for running multiple 'release' targets in parallel?

There doesn't need to be one - other than two developers on the same machine trying to do builds.
Hard coded paths like /var/tmp/temproot are always a problem in such cases.

[gjb]

In D3002#86262, @sjg wrote:

In D3002#86258, @gjb wrote:

Implementation question: What is the use case for running multiple 'release' targets in parallel?

There doesn't need to be one - other than two developers on the same machine trying to do builds.
Hard coded paths like /var/tmp/temproot are always a problem in such cases.

This makes sense, thank you.

Simon, I will defer to you for the proper solution here, as it seems you already have proposed one.