Fix running & building under macOS (Big Sur) (#9)

* Add xcbuild as native build input 2 ways & pass --verbose to cargo build

* Make "deploy" build on macOS

* Bump the nixpkgs version to one that ships Rust 1.47, which can
  produce binaries under macOS 11 (Big Sur).

* Use darwin-specific options that let Naersk build the "deploy"
  binary under macOS. (With a work-around for
  https://github.com/nmattia/naersk/issues/127, which prevents this
  from being much more straight-forward).

Unfortunately, the "activate" binary can't be built under macOS due to
the inotify dependency; that means the best we can do is to run the
deploy under macOS, not deploy *to* macOS.

2 files changed, 17 insertions, 7 deletions

diff --git a/flake.lock b/flake.lock
index c9e4ff3..e5b7ffe 100644
--- a/flake.lock
+++ b/flake.lock
@@ -39,11 +39,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1601961544,
-        "narHash": "sha256-uuh9CkDWkXlXse8IcergqoIM5JffqfQDKsl1uHB7XJI=",
+        "lastModified": 1605716121,
+        "narHash": "sha256-CbHicvkzLTfEY+aSUeUY7dfFlDOgZH3uK+PpUfb/DPA=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "89281dd1dfed6839610f0ccad0c0e493606168fe",
+        "rev": "6625284c397b44bc9518a5a1567c1b5aae455c08",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index d92a60a..2e775ca 100644
--- a/flake.nix
+++ b/flake.nix
@@ -23,10 +23,20 @@
       let
         pkgs = import nixpkgs { inherit system; };
         naersk-lib = pkgs.callPackage naersk { };
+        isDarwin = pkgs.lib.strings.hasSuffix "-darwin" system;
+        darwinOptions = pkgs.lib.optionalAttrs isDarwin {
+          nativeBuildInputs = [
+            pkgs.darwin.apple_sdk.frameworks.SystemConfiguration
+          ];
+          singleStep = true; # https://github.com/nmattia/naersk/issues/127
+          cargoBuildOptions = opts: opts ++ [ "--bin" "deploy" ]; # The "activate" binary is linux-only.
+        };
       in
       {
         defaultPackage = self.packages."${system}".deploy-rs;
-        packages.deploy-rs = naersk-lib.buildPackage ./.;
+        packages.deploy-rs = naersk-lib.buildPackage (darwinOptions // {
+          root = ./.;
+        });
 
         defaultApp = self.apps."${system}".deploy-rs;
         apps.deploy-rs = {
@@ -35,9 +45,9 @@
         };
 
         devShell = pkgs.mkShell {
-            inputsFrom = [ self.packages.${system}.deploy-rs ];
-            buildInputs = [ pkgs.nixUnstable ];
-          };
+          inputsFrom = [ self.packages.${system}.deploy-rs ];
+          buildInputs = [ pkgs.nixUnstable ];
+        };
 
         lib = rec {