gcc: revert "do not install sys-include headers for cross-compilers."

[trofi]

The change reverts commit 7df4387

A few reasons to revert the commit:

1. The change was not enough to restore -idirafter override semantic to match unwrapped compiler.
2. The change broke override semantics for cross-compilers
3. The change made override semantics different between cross-compiler and native compiler

All of three have some overlap between, but I think it's important to call all of them out.

The main fallout is the uboot builds, reported by cynerd.

Used the following test to check the override recovery:

$ nix shell github:NixOS/nixpkgs/release-22.05#pkgsCross.aarch64-multiplatform.stdenv.cc
$$ cat stdio.h
# empty
$$ printf "#include <stdio.h>" | aarch64-unknown-linux-gnu-gcc -E - -o - -idirafter . >/dev/null; echo $?
0

It failed before the change and succeded after.

Description of changes

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)
• 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/)
• 23.11 Release Notes (or backporting 23.05 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.

[trofi]

Validated the fix helped for a smaller test:

$ nix shell -f. pkgsCross.aarch64-multiplatform.stdenv.cc
$$ touch stdio.h
$$ printf "#include <stdio.h>" | aarch64-unknown-linux-gnu-gcc -E - -o - -idirafter . >/dev/null; echo $?
0

[trofi]

And also tested on @Cynerd 's config as:

$ nix build .#legacyPackages.x86_64-linux.pkgsCross.aarch64-multiplatform.ubootTurrisMox --override-input nixpkgs ~/patched-staging

The change recovered the build.

[ghost]

This is a very good idea. Especially because the conditional can't be known at eval-time, so this if-then-fi can't be lifted into Nix code.

I will merge this as soon as my rebuilds complete.

Building on:

• x86_64-linux
• powerpc64le-linux
• aarch64-linux (cross from x86_64-linux)
• mips64el-linux mixed n32/64 (cross from x86_64-linux)

Also built:

• pkgs.tests.cross.sanity (almost finished)

[trofi]

Caused bootstrap failure on aarch64-linux: #246147 .Looks like it exposed use of old libgcc against new libstdc++ headers.

[ghost]

Caused bootstrap failure on aarch64-linux: #246147 .Looks like it exposed use of old libgcc against new libstdc++ headers.

This turned out to be due to parallel stripping, rather than libgcc:

• setup-hooks/strip: resolve/uniq symlinks before stripping #246164