closures of cross packages include build packages

[goertzenator]

Issue description

A closure for a cross compiled packages includes all the build packages:

$ nix build -f channel:nixos-unstable pkgsCross.raspberryPi.hello
$ nix-store -qR result
/nix/store/xdsjx0gba4id3yyqxv66bxnm2sqixkjj-glibc-2.27
/nix/store/xiypl4ghzm03dmss75kgzf2l4c8lz06g-attr-2.4.47
/nix/store/7q93f42w9snblrim7qqly9rkk57j9hhv-acl-2.2.52
/nix/store/0q4i5ll9gxs6giq7kqkniww934j9j8dk-coreutils-8.30
/nix/store/x6inizi5ahlyhqxxwv1rvn05a25icarq-gcc-7.3.0-lib
/nix/store/9yb6gizxpll4l6gf7md75kbii6b1dvjc-gmp-6.1.2
/nix/store/1pzd4h9ixc4z61zys4rf7jxhwzrcyzwj-gmp-6.1.2-dev
/nix/store/22lrlr8d1d0dymy29jfpgmksfx1p5kc6-glibc-2.27-bin
/nix/store/nsrwlly5ikwhppcslaazp547kh7q7j6s-zlib-1.2.11
/nix/store/c90akqjk2lk9r18wvxnkvd07j2nnl3f1-linux-headers-4.18.3
/nix/store/psqblh5bsgkbkhn4r648pgjw5rq4npkv-glibc-2.27-dev
/nix/store/p7j7qg5cri229ihf8nllwjhzgbvgx5d0-gcc-7.3.0
/nix/store/2nrwba2rahwka6pz6354xza1mnb1dd5v-armv6l-unknown-linux-gnueabihf-stage-static-gcc-debug-7.3.0-lib
/nix/store/a50sg2xm6vflzx5kma3sih39dq9wv7z6-zlib-1.2.11-dev
/nix/store/3hrh50f5gqxg2hi9aczmswwvx7k7m040-armv6l-unknown-linux-gnueabihf-binutils-2.30
/nix/store/5kqyp2ipi39r7j50ri2lh4ikkw3f6ypw-expand-response-params
/nix/store/can00lfiynqkbsdkkmgp6qg8p8w92cxa-bash-4.4-p23
/nix/store/9094wvfc40rgnszk8r31l6vvr1ahg9hb-armv6l-unknown-linux-gnueabihf-binutils-wrapper-2.30
/nix/store/vn8g3p4rn8xbqmwzfs5ic2pmzldaijss-mpfr-4.0.1
/nix/store/a8fx8f5cwr8n9rzms700pabr30w23amz-libmpc-1.1.0
/nix/store/bvn1405cf45bs3il2f4mncwjxnjgrpkw-isl-0.17.1
/nix/store/ij6ygcnk6qmymaa4p6f2d54dxygpl5hm-linux-headers-4.18.3
/nix/store/nsggkr1m85mqdifrbddb7pmvgs2jjp73-mpfr-4.0.1-dev
/nix/store/zk2g34m3bdya2v7vxaqapmb2v49ihqlc-armv6l-unknown-linux-gnueabihf-stage-static-gcc-debug-7.3.0
/nix/store/hs5nhrhy9i1g0mzjss9pyamxacsc46jz-glibc-2.27-armv6l-unknown-linux-gnueabihf
/nix/store/kviifpyj4n081avgh0rmns3rmmz8p2rd-hello-2.10-armv6l-unknown-linux-gnueabihf

Cross-compiled closures are useful for deploying to compact embedded systems, so bringing all this baggage is a show stopper. For reference, a non-cross compiled package has minimal dependencies:

$ nix build -f channel:nixos-unstable hello
$ nix-store -qR result
/nix/store/xdsjx0gba4id3yyqxv66bxnm2sqixkjj-glibc-2.27
/nix/store/85s7px3vlr8adrk200292y7rxpdnzs4j-hello-2.10

Technical details

Please run nix-shell -p nix-info --run "nix-info -m" and paste the
results.

 - system: `"x86_64-linux"`
 - host os: `Linux 4.14.87, NixOS, 18.09.1625.b352d47e42b (Jellyfish)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.1.3`
 - channels(root): `"nixos-18.09.1625.b352d47e42b, unstable-18.03pre130569.7a04c2ca296"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[FRidh]

This is a known issue. This requires tracking what packages don't clean up their references. As there are potential a lot (cross-compiling hasn't gotten much attention yet) I don't see much point in keeping an issue open for it so I am closing it (for now).

[goertzenator]

Are there related issues that you could point me to so I can learn more? Is this a package by package tidy-up or central infrastructure to do this automatically?

[FRidh]

Regarding Python I'll be looking at #53320. Aside from that, there have been a couple of people working on the infrastructure. That is now in place, though some improvements are needed, such as patchShebangs #33956.

But regarding the issue you've raised. It's matter of fixing expressions. They've never been written with cross-compilation in mind.

[danbst]

GCC doesn't strip in cross-compilation variant:
https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/compilers/gcc/8/default.nix#L22-L24