travis-ci: attempt to fix linux builds

[domenkozar]

From #16013 (comment):

Travis on Linux is still broken from around the time it was last touched by adding the Darwin support. (Looks like /tmp is now noexec or something). Please investigate.

[mention-bot]

By analyzing the blame information on this pull request, we identified @wmertens, @dezgeg and @madjar to be potential reviewers

[dezgeg]

Thanks!

[joachifm]

Still seeing spurious failures, e.g., https://travis-ci.org/NixOS/nixpkgs/jobs/136399016

[joachifm]

Looks to me like many (all?) builds that require executable permissions still fail. Any word from upstream on what could be the reason?

[domenkozar]

@joachifm for example?

[joachifm]

In addition to the one I've already linked, the following are some examples of what I'm talking about:

https://travis-ci.org/NixOS/nixpkgs/jobs/137042231
https://travis-ci.org/NixOS/nixpkgs/jobs/137813075
https://travis-ci.org/NixOS/nixpkgs/jobs/136596056
https://s3.amazonaws.com/archive.travis-ci.org/jobs/137450214/log.txt
https://travis-ci.org/NixOS/nixpkgs/jobs/137155162
https://travis-ci.org/NixOS/nixpkgs/jobs/137174436

[joachifm]

Almost every submission is now in the red, which means either travis got better at detecting errors, submission quality tanked, or it's erroring out too much to be useful. My impression leans more towards the latter.

[joachifm]

Looks like 5b7c6a1 may have done the trick; I restarted https://travis-ci.org/NixOS/nixpkgs/jobs/138028096 and it now works.