Fix build on Nix 2.19+

Nix 2.19 introduced a change [0] that broke how we compile our libnixstore
bindings, which requires adding an additional include directory when
we compile them.

[0]: NixOS/nix@b461cac

attic/build.rs

@@ -24,6 +24,9 @@ fn build_bridge() {
         .flag("nix/config.h")
         .flag("-idirafter")
         .flag(hacky_include.path().to_str().unwrap())
+        // In Nix 2.19+, nix/args/root.hh depends on being able to #include "root.hh" (which is in its parent directory), for some reason
+        .flag("-I")
+        .flag(concat!(env!("NIX_INCLUDE_PATH"), "/nix"))
         .compile("nixbinding");
 
     println!("cargo:rerun-if-changed=src/nix_store/bindings");

crane.nix

@@ -62,6 +62,9 @@ let
 
     ATTIC_DISTRIBUTOR = "attic";
 
+    # See comment in `attic/build.rs`
+    NIX_INCLUDE_PATH = "${lib.getDev nix}/include";
+
     # See comment in `attic-tests`
     doCheck = false;
 
@@ -136,6 +139,9 @@ let
     checkPhaseCargoCommand = "cargoWithProfile test --no-run --message-format=json >cargo-test.json";
     doInstallCargoArtifacts = false;
 
+    # See comment in `attic/build.rs`
+    NIX_INCLUDE_PATH = "${lib.getDev nix}/include";
+
     installPhase = ''
       runHook preInstall
 

flake.nix

@@ -130,6 +130,9 @@
         NIX_PATH = "nixpkgs=${pkgs.path}";
         RUST_SRC_PATH = "${pkgs.rustPlatform.rustcSrc}/library";
 
+        # See comment in `attic/build.rs`
+        NIX_INCLUDE_PATH = "${lib.getDev pkgs.nix}/include";
+
         ATTIC_DISTRIBUTOR = "dev";
       };
 

package.nix

@@ -49,6 +49,9 @@ in rustPlatform.buildRustPackage rec {
 
   ATTIC_DISTRIBUTOR = "attic";
 
+  # See comment in `attic/build.rs`
+  NIX_INCLUDE_PATH = "${lib.getDev nix}/include";
+
   # Recursive Nix is not stable yet
   doCheck = false;