Convert posix scripts to bash

[Daniel-Worrall]

This addresses #31036

Additional PRs for this issue are in their respective repos:

• Convert posix scripts to bash stdarch#853
• Convert posix scripts to bash miri#1395
• Convert posix scripts to bash rust-installer#102

Files not converted are:

• src/tools/clippy/util/dev (This is deprecated)
• src/tools/rust-installer/test/image1/bin/program
• src/tools/rust-installer/test/image1/bin/program2
• src/tools/rust-installer/test/image1/bin/oldprogram
• src/tools/rust-installer/test/image1/bin/cargo

All except the first are single-lined files that hold just #!/bin/sh

[rust-highfive]

r? @kennytm

(rust_highfive has picked a reviewer for you, use r? to override)

[Dylan-DPC-zz]

r? @Dylan-DPC

[Mark-Simulacrum]

The internal scripts are probably fine to convert here but I'm not sure about the external-facing scripts (e.g. rust-gdb and configure) -- those will need some analysis of the platforms we support and whether bash is available on them out of the box.

[RalfJung]

The last activity in that issue was almost 3 years ago, and I see no clear team consensus for replacing #!/bin/sh by #!/bin/sh -- the last message is a plan/request for gathering more data.

So before changing anything I'd suggest we determine if there is consensus for the change.

[Daniel-Worrall]

As for internal/external scripts, stdarch & rust-installer PRs hold internal script changes, and miri holds an external script change.

[raphaelcohn]

Please, for the love of everything, keep scripts as POSIX and not bash. bash is a pig, it's not as commonly installed as one might think and build systems should make as few assumptions of build environment as possible. Complex build environments are responsible for many, many defects over the years.

bash is not installed by default even on modern Linux setups, eg Alpine. It's got a nasty history of security defects, and, if building from scratch to make a reproducible system, makes far too many assumptions and requires far too many other dependencies.

[Mark-Simulacrum]

I'm going to nominate this for the infra team, but I myself am inclined to close this -- I just don't think we're really in need of this change right now (to my knowledge the scripts have not faced any significant maintenance burden) and I don't think we have the time/ability to properly evaluate the breakage (or lack thereof) this could cause.

[Dylan-DPC-zz]

r? @Mark-Simulacrum

[Mark-Simulacrum]

We discussed this at the last infrastructure team meeting and felt that there was not currently bandwidth in the team to properly evaluate this change. Specifically, we want to do a survey of various platforms to determine the best shell (if there is one) to use. It was also brought up that we would generally accept fixes to our shell code if there are minor changes that would make it compatible with a wider variety of shells, but that changing the shebang is unlikely to be helpful -- in particular, it seems like finding a shebang that will actually exist and be consistent across all platforms isn't likely.

With that in mind, I'm going to go ahead and close this PR. I personally would prefer to close the issue that spawned it as well, since I don't expect us to do anything here unless there's active interest in changing things (and then having an issue open seems like it brings no benefit). But I don't know that we have consensus on that so not going to close it.

Thanks @Daniel-Worrall!