Add shells/*

Signed-off-by: Ivan Bushchik <ivabus@ivabus.dev>

README.md

@@ -24,9 +24,13 @@ Apple Silicon hosts require additional `--impure` flag for firmware installation
 - vetus (iMac 27" 2017)
 - celerrime (MacBook Air M2)
 
+## Shells
+
+I "made" some shell in [shells/](./shells).
+
 ## Dotfiles (from `ivabus/dotfiles`)
 
-I'm installing my dotfiles using (with prepared script)
+I install my dotfiles with prepared script
 
 ```shell
 curl https://iva.bz/nix | sh

shells/README.md

@@ -0,0 +1,13 @@
+# Shells
+
+- `crossShell.nix` - Just useful shell for cross compiling
+
+## Using
+
+```
+nix-shell PATH_TO_SHELL
+```
+
+### `crossShell.nix`
+
+By default configured for `aarch64-unknown-linux-musl`, but target may be replaced by adding crossSystem arg, like `--argstr crossSystem "x86_64-unknown-linux-musl"`.

shells/crossShell.nix

@@ -0,0 +1,15 @@
+{ crossSystem ? "aarch64-unknown-linux-musl" }:
+
+let pkgs = import <nixpkgs> {
+  crossSystem = {
+    config = crossSystem;
+  };
+};
+in
+  pkgs.callPackage (
+    {mkShell, pkg-config, zlib}:
+    mkShell {
+      nativeBuildInputs = [ pkg-config ];
+      buildInputs = [ zlib ];
+    }
+  ) {}