cross work

crossArgs.nix

@@ -0,0 +1,38 @@
+{ callPackage, pkgsCross, stdenv, lib }:
+let
+  inherit (lib) mapAttrs hasInfix replaceStrings toUpper concatStrings recursiveUpdate;
+  isMusl = hasInfix "-musl";
+  crossOpts = callPackage ./crossOpts.nix { };
+
+  buildCrossArgs = target: { targetDeps ? [ ]
+                           , rustFlags ? (if isMusl target then "-C target-feature=+crt-static" else "")
+                           , cFlags ? ""
+                           , targetStdenv
+                           , ...
+                           } @ args:
+    let
+      isHostTarget = targetStdenv.targetPlatform.config == stdenv.targetPlatform.config;
+      # don't use the pkgsCross cc if the target is the host platform
+      targetCc = if isHostTarget then stdenv.cc else targetStdenv.cc;
+      targetUnderscore = replaceStrings [ "-" ] [ "_" ] target;
+      targetUpperCase = toUpper targetUnderscore;
+      rest = removeAttrs args [ "rustFlags" "cc" "cFlags" "targetDeps" "targetStdenv" "nativeBuildInputs" ];
+      # by adding the dependency in the (target specific) linker args instead of buildInputs
+      # we can prevent it trying to link to it for host build dependencies
+      rustFlagsWithDeps = rustFlags + concatStrings (map (targetDep: " -Clink-arg=-L${targetDep}/lib") targetDeps);
+    in
+    (
+      {
+        nativeBuildInputs = (args.nativeBuildInputs or [ ]) ++ [ targetCc stdenv.cc ];
+        "CARGO_TARGET_${targetUpperCase}_RUSTFLAGS" = rustFlagsWithDeps;
+        "CARGO_TARGET_${targetUpperCase}_LINKER" = "${targetCc.targetPrefix}cc";
+        "AR_${targetUnderscore}" = "${targetCc.targetPrefix}ar";
+        "CC_${targetUnderscore}" = "${targetCc.targetPrefix}cc";
+        "CCX_${targetUnderscore}" = "${targetCc.targetPrefix}ccx";
+        "HOST_CC" = "${stdenv.cc.targetPrefix}cc";
+        "CFLAGS_${targetUnderscore}" = cFlags;
+      } //
+      rest
+    );
+in
+target: buildCrossArgs target crossOpts.${target}