[Backport release-23.11] swift: force-unwrap file handles in swift-tools-support-core

[donn]

Description of changes

This backports #269015 to release-23.11, as without these patches, the Swift programming language is broken on 23.11

Affected derivations are:

• swiftpm
• sourcekit-lsp
• swift-format
• swift-driver

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• 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/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 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.

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[finagolfin]

Do you mind trying my upstream pull instead? swiftlang/swift-tools-support-core#457

[donn]

I didn't author this PR, I'm merely backporting it.

That said, may not be a bad idea to create a PR with your patch for master

[donn]

I suppose there's no point keeping this open for much longer given 24.05 is on the horizon.