nix: Add a shell.nix file

This works for me on NixOS 22.05.

Author: gnprice

shell.nix

@@ -0,0 +1,54 @@
+# All our non-NPM dependencies and dev-dependencies, expressed with Nix.
+#
+# TODO: Expand this to cover the full Android dev environment,
+#   and everything in tools/.
+#
+# If you're using NixOS, this file may be helpful:
+#  * Type `nix-shell` in this directory.
+#  * You'll get a shell with the environment all set up
+#    so that `yarn install` and `tools/test --all` work.
+#  * Also `android-studio`, and from there you can run the
+#    Android emulator and build and run the app:
+#    * Start emulator from Android Studio.
+#    * Run `adb reverse tcp:8081 tcp:8081` in the shell.
+#    * Run `node_modules/.bin/react-native start` in the shell.
+#    * Run the app from Android Studio.
+#
+# If you're using any other Linux distro, or macOS, or Windows, see
+# our setup instructions at `docs/howto/build-run.md`.  But possibly
+# this is a useful reference for some of our dependencies.  (Note
+# that you almost certainly already have the more obscure of these
+# dependencies already, namely ncurses and the C++ standard library.)
+
+# For developing changes to this file, use `nix-shell --pure --run`
+# to check that the dependencies here are complete, without relying
+# on things that happen to be in your local environment.  E.g.:
+#
+#   $ nix-shell --pure --run 'yarn && tools/test --all'
+
+{ pkgs ? import <nixpkgs> {} }:
+with pkgs;
+mkShell {
+
+  nativeBuildInputs = [
+    nodejs-16_x
+    yarn
+
+    jdk11
+    android-studio
+
+    # Used by various `tools/` scripts:
+    git
+    jq
+    perl
+    rsync
+
+    ncurses  # Used by Flow (via the `tset` binary)
+
+    vscode
+  ];
+
+  LD_LIBRARY_PATH = lib.makeLibraryPath [
+    gcc11.cc  # Needed by Flow (the one from NPM.)
+  ];
+}