misc: add nix flake, toolchain config

Author: rrbutani

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -88,3 +88,6 @@ $RECYCLE.BIN/
 
 # Windows shortcuts
 *.lnk
+
+# Nix
+.direnv/

flake.lock

@@ -0,0 +1,36 @@
+{
+  description = "UTP TM4C Flake";
+
+  inputs = {
+    nixpkgs.url      = github:NixOS/nixpkgs/nixos-21.11;
+    rust-overlay.url = github:oxalica/rust-overlay;
+    flake-utils.url  = github:numtide/flake-utils;
+  };
+
+  # TODO: cargo extensions
+  # TODO: CI setup? (garnix)
+  # TODO: expose targets, etc.
+  # TODO: flip-link, tests, etc.
+
+  # TODO: openocd, gdb-dashboard, etc.
+
+  outputs = { self, nixpkgs, rust-overlay, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        overlays = [ (import rust-overlay) ];
+        pkgs = import nixpkgs {
+          inherit system overlays;
+        };
+      in
+      with pkgs;
+      {
+        devShells.default = mkShell {
+          buildInputs = [
+            (rust-bin.fromRustupToolchainFile ./rust-toolchain.toml)
+          ];
+          shellHook = ''
+          '';
+        };
+      }
+    );
+}

flake.nix

@@ -0,0 +1,4 @@
+[toolchain]
+channel = "1.61.0"
+components = [ "rustc", "cargo", "rustfmt", "rust-std", "rust-docs", "rustc-dev", "clippy", "rust-src", "llvm-tools-preview" ]
+targets = [ "thumbv7em-none-eabihf" ]