treewide: drop flattenInclude hack

[K900]

This may have been relevant 10 years ago ([DOUBT]), but it sure as hell isn't now, and recursive symlinks are evil.

May it burn in hell, as that is where it belongs.

I've built both Qt versions and all three GTKs, which should hopefully contain most of the blast radius, but there's definitely a chance of a lot of random leaf packages breaking here, so I'm not sure if we want to rush it in before 24.11.

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/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 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.

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[SuperSandro2000]

Does this cause issues or is just a cleanup? If the later we could just schedule it for next stable to be on the chilled side.

[K900]

Technically, it can cause issues. In practice, I really doubt it will.

[vcunat]

I get that it solves the linked issue, too? (an argument to have this PR in 24.11)

[K900]

For this specific package, yes. Generally, this is a buildEnv / symlink loops issue, and I think the endgame should be to just ban symlink loops treewide.

[K900]

@ofborg eval

[K900]

@ofborg eval

[trofi]

Bisect says 54874b3 treewide: drop flattenInclude hack broke at least dmenu on staging as:

$ nix build --no-link -f. dmenu -L
...
dmenu> build flags: SHELL=/nix/store/mm0pa3z7kk6jh1i9rkxqxjqmd8h1qpxf-bash-5.2p37/bin/bash CC:=\$\(CC\)
dmenu> cp config.def.h config.h
dmenu> gcc -c -std=c99 -pedantic -Wall -Os -I/usr/X11R6/include -I/usr/include/freetype2 -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D_POSIX_C_SOURCE=200809L -DVERSION=\"5.3\" -DXINERAMA dmenu.c
dmenu> In file included from dmenu.c:17:
dmenu> /nix/store/2rxphcg0qabc3a8c4lvy610sm03bh72y-libXft-2.3.8-dev/include/X11/Xft/Xft.h:40:10: fatal error: ft2build.h: No such file or directory
dmenu>    40 | #include <ft2build.h>
dmenu>       |          ^~~~~~~~~~~~
dmenu> compilation terminated.
dmenu> make: *** [Makefile:12: dmenu.o] Error 1

[trofi]

Proposed dmenu fix as:

• dmenu: fix build on staging-next #348884