rust/cargo.nix: set HOST_PKG_CONFIG_PATH for cross builds

Prior to this commit, builds of
`pkgsCross.aarch64-multiplatform.cargo` would fail due to being
unable to find `-lz` when compiling cargo's own `build.rs` for the
`buildPlatform`.

This environment variable uses the (very confusing) LLVM convention
of calling the buildPlatform "HOST".

Co-authored-by: figsoda <figsoda@pm.me>

2 files changed, 8 insertions, 6 deletions

diff --git a/pkgs/development/compilers/rust/cargo-auditable.nix b/pkgs/development/compilers/rust/cargo-auditable.nix
index 49968cc899b..dbbfff4dc6b 100644
--- a/pkgs/development/compilers/rust/cargo-auditable.nix
+++ b/pkgs/development/compilers/rust/cargo-auditable.nix
@@ -1,6 +1,4 @@
-{ lib
-, stdenv
-, fetchFromGitHub, makeRustPlatform, rustc, cargo, installShellFiles }:
+{ lib, fetchFromGitHub, makeRustPlatform, rustc, cargo, installShellFiles, stdenv }:
 
 let
   args = rec {
diff --git a/pkgs/development/compilers/rust/cargo.nix b/pkgs/development/compilers/rust/cargo.nix
index 705d172e4fc..beb1912658c 100644
--- a/pkgs/development/compilers/rust/cargo.nix
+++ b/pkgs/development/compilers/rust/cargo.nix
@@ -1,14 +1,15 @@
 { lib, stdenv, pkgsBuildHost, pkgsHostHost
 , file, curl, pkg-config, python3, openssl, cmake, zlib
-, installShellFiles, makeWrapper, rustPlatform, rustc
+, installShellFiles, makeWrapper, rustPlatform, rust, rustc
 , CoreFoundation, Security
 , auditable ? !cargo-auditable.meta.broken
 , cargo-auditable
+, pkgsBuildBuild
 }:
 
-rustPlatform.buildRustPackage.override (lib.optionalAttrs (!cargo-auditable.meta.broken) {
+rustPlatform.buildRustPackage.override {
   cargo-auditable = cargo-auditable.bootstrap;
-}) {
+} ({
   pname = "cargo";
   inherit (rustc) version src;
 
@@ -113,3 +114,6 @@ rustPlatform.buildRustPackage.override (lib.optionalAttrs (!cargo-auditable.meta
     platforms = platforms.unix;
   };
 }
+// lib.optionalAttrs (rust.toRustTarget stdenv.buildPlatform != rust.toRustTarget stdenv.hostPlatform) {
+  HOST_PKG_CONFIG_PATH="${pkgsBuildBuild.pkg-config}/bin/pkg-config";
+})