shaderc: move to by-name, unvendor glslang, 2025.3 -> 2025.5

[marcin-serwin]

Depends on #477412

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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[philiptaron]

Changes look good to me, doing a build (of Ghostty)

[philiptaron]

nixpkgs-review result

Generated using nixpkgs-review.

Command: nixpkgs-review pr 477464 --package ghostty
Commit: 401c6239203fcf984b57e0b0002c90f297d39476

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x86_64-linux

✅ 5 packages built:

• ghostty
• ghostty.man (ghostty.man.man, ghostty.man.shell_integration, ghostty.man.terminfo, ghostty.man.vim)
• ghostty.shell_integration (ghostty.shell_integration.man, ghostty.shell_integration.shell_integration, ghostty.shell_integration.terminfo, ghostty.shell_integration.vim)
• ghostty.terminfo (ghostty.terminfo.man, ghostty.terminfo.shell_integration, ghostty.terminfo.terminfo, ghostty.terminfo.vim)
• ghostty.vim (ghostty.vim.man, ghostty.vim.shell_integration, ghostty.vim.terminfo, ghostty.vim.vim)

[K900]

This broke ffmpeg_full builds, specifically tests fail to link with

┃        > /nix/store/nki6kv8c7ljlcgvihm7xnwrqi8i49cvn-binutils-2.44/bin/ld: libavfilter/libavfilter.a(vulkan_shaderc.o): undefined reference to symbol 'shaderc_compile_options_initialize'
┃        > /nix/store/nki6kv8c7ljlcgvihm7xnwrqi8i49cvn-binutils-2.44/bin/ld: /nix/store/bf5s4smqcx5vhb6jvwdcd3502lfq2dql-shaderc-2025.5-lib/lib/libshaderc_shared.so.1: error adding symbols: DSO missing from command line

Or similar. I'm going to skip the tests for ffmpeg builds with shaderc for now, but we'll want a better solution.