Fix shellcheck SC2148 and SC1008

[l0b0]

Motivation for this change

Existing issues requesting ShellCheck compliance: #133088, #21166.

This change only prepares for running ShellCheck by indicating which shell ShellCheck should interpret the code (Bash). The same can also be achieved by renaming the scripts to .bash, but that would be much more involved and risky, possibly including changes to other repos which reference scripts by name.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual) N/A
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/) N/A
• 21.11 Release Notes (or backporting 21.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[l0b0]

I've set this as a draft, for several reasons:

• Most importantly, a better solution would be to rename the files from .sh to .bash, which would clearly indicate to anyone reading it (including tools like ShellCheck) that the shell dialect matters, and that programmers should feel free to use bashisms to improve maintainability, speed, etc.
• Someone could fairly easily create one PR per package, which would be much easier to get merged individually.
• There seems to be no clear standard for shebang lines in this project. Some scripts seem to use #!/bin/sh when they shouldn't, because they contain bashisms. Others use #!/usr/bin/env bash, #!/usr/bin/env nix-shell plus #!nix-shell -i bash -p …, others again use #!@shell@ or #!@runtimeShell@. I don't know whether all of these forms are helpful, and if so, when they should each be used.

[Et7f3]

#!@runtimeShell@ Allow to resolve bash at build time. So for wrapper I would prefer using that. For independant script that will not be rebuild /usr/bin/env bash seem better because it choose bash at runtime. #!/usr/bin/env nix-shell with --pure is even better because it show explicitly dependencies of a script but require more work to use this style so just usign env is fine if you only need tools in stdenv like sed/find/cat/cd/mv/...