treewide: skip generating shell completions using $out/bin/… when cross compiling

This focuses on Rust packages, since the most commonly used argument
parser library (clap/structopt) makes the following pattern natural and
thus common:

  postInstall = ''
    installShellCompletion --cmd foo \
      --bash <($out/bin/foo completion bash) \
      …

This commit just guards those with

lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform)

splitting the string where unrelated actions are performed.

1 files changed, 1 insertions, 1 deletions

diff --git a/pkgs/by-name/as/ast-grep/package.nix b/pkgs/by-name/as/ast-grep/package.nix
index 644ef2e284ca..ab33df30035a 100644
--- a/pkgs/by-name/as/ast-grep/package.nix
+++ b/pkgs/by-name/as/ast-grep/package.nix
@@ -25,7 +25,7 @@ rustPlatform.buildRustPackage rec {
     rm .cargo/config.toml
   '';
 
-  postInstall = ''
+  postInstall = lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''
     installShellCompletion --cmd sg \
       --bash <($out/bin/sg completions bash) \
       --fish <($out/bin/sg completions fish) \