feat(users/Profpatsch): add a tree-sitter parser for nix

Uses the rust library to set up a simple nix parsing expression, which
reads a nix file and prints the sexp tree.

Change-Id: I32dc9c7b39aa0f7ffa2b99348d6c2269e5fe1a6a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2402
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

users/Profpatsch/rust-crates.nix

@@ -0,0 +1,53 @@
+{ depot, pkgs, ... }:
+rec {
+  cfg-if = pkgs.buildRustCrate {
+    pname = "cfg-if";
+    crateName = "cfg-if";
+    version = "1.0.0";
+    sha256 = "1fzidq152hnxhg4lj6r2gv4jpnn8yivp27z6q6xy7w6v0dp6bai9";
+  };
+
+  cc = pkgs.buildRustCrate {
+    pname = "cc";
+    crateName = "cc";
+    version = "1.0.66";
+    sha256 = "12q71z6ck8wlqrwgi25x3lrryyks9djymswn9b1c6qq0i01jpc1p";
+  };
+
+  regex-syntax = pkgs.buildRustCrate {
+    pname = "regex-syntax";
+    crateName = "regex-syntax";
+    version = "0.6.22";
+    sha256 = "0r00n2dgyixacl1sczqp18gxf0xh7x272hcdp62412lypba2gqyg";
+  };
+
+  regex = pkgs.buildRustCrate {
+    pname = "regex";
+    crateName = "regex";
+    version = "1.4.3";
+    features = [ "std" ];
+    dependencies = [ regex-syntax ];
+    sha256 = "0w0b4bh0ng20lf5y8raaxmxj46ikjqpgwy1iggzpby9lhv9vydkp";
+  };
+
+  libloading = pkgs.buildRustCrate {
+    pname = "libloading";
+    crateName = "libloading";
+    version = "0.6.7";
+    dependencies = [ cfg-if ];
+    sha256 = "111d8zsizswnxiqn43vcgnc2ym9spsx1i6pcfp35ca3yw2ixq95j";
+  };
+
+  tree-sitter = pkgs.buildRustCrate {
+    pname = "tree_sitter";
+    crateName = "tree-sitter";
+    # buildRustCrate isn’t really smart enough to detect the subdir
+    libPath = "binding_rust/lib.rs";
+    # and the build.rs is also not where buildRustCrate would find it
+    build = "binding_rust/build.rs";
+    version = "0.17.1";
+    dependencies = [ regex ];
+    buildDependencies = [ cc ];
+    sha256 = "0jwwbvs4icpra7m1ycvnyri5h3sbw4qrfvgnnvnk72h4w93qhzhr";
+  };
+}