build: download tree sitter sources in dune

Moves the download step to dune rules, allowing us to eliminate an extra
script. This also means dune is aware of the archive, so can handle
caching it directly (understanding a version change invalidates it)
without the need for a script to handle this logic.

Author: kopecs

dune

@@ -1,13 +1,25 @@
 (dirs :standard)
 
+(rule
+ (action
+  (with-stdout-to
+   tree-sitter-sources.tgz
+   (run
+    curl
+    -L
+    https://github.com/tree-sitter/tree-sitter/archive/refs/tags/v%{read-lines:tree-sitter-version}.tar.gz))))
+
 (rule
  (mode
   (promote (until-clean)))
- (deps tree-sitter-version)
  (target
   (dir tree-sitter-repo))
+ (deps
+  (:source-archive tree-sitter-sources.tgz))
  (action
-  (run %{project_root}/scripts/download-tree-sitter %{target})))
+  (progn
+   (run mkdir -p %{target})
+   (run tar xf %{source-archive} -C %{target} --strip-components=1))))
 
 (rule
  (deps tree-sitter-repo)