tmp directories should be dynamic in build scripts

[Matthew Mosesohn]

I ran into an issue where I built the ISO from one account and then another account, but /tmp/static_compressed couldn't be accessed because of the files created by the previous build process.

We should always rely on mktemp if we need to place any temporary data in /tmp, instead of using the same directory. It also increases security of the build when running on a multi user system.

[Dmitry Pyzhov (dpyzhov)]

Makesystem should not write anything to /tmp. This particular bug is fixed here: https://review.openstack.org/#/c/91348/