llvmPackages_rocm: add update script

pkgs/development/compilers/llvm/rocm/llvm/default.nix

@@ -1,6 +1,7 @@
 { stdenv
 , lib
 , fetchFromGitHub
+, writeScript
 , cmake
 , python3
 , libxml2
@@ -88,6 +89,23 @@ in stdenv.mkDerivation rec {
 
   passthru.src = src;
 
+  updateScript = writeScript "update.sh" ''
+    #!/usr/bin/env nix-shell
+    #!nix-shell -i bash -p curl jq common-updater-scripts nix-prefetch-github
+
+    version="$(curl -sL "https://api.github.com/repos/RadeonOpenCompute/llvm-project/releases?per_page=1" | jq '.[0].tag_name | split("-") | .[1]' --raw-output)"
+    current_version="$(grep "version =" pkgs/development/compilers/llvm/rocm/default.nix | cut -d'"' -f2)"
+    if [[ "$version" != "$current_version" ]]; then
+      tarball_meta="$(nix-prefetch-github RadeonOpenCompute llvm-project --rev "rocm-$version")"
+      tarball_hash="$(nix to-base64 sha256-$(jq -r '.sha256' <<< "$tarball_meta"))"
+      sed -i "pkgs/development/compilers/llvm/rocm/default.nix" \
+        -e 's,version = "\(.*\)",version = "'"$version"'",' \
+        -e 's,hash = "\(.*\)",hash = "sha256-'"$tarball_hash"'",'
+    else
+      echo rocm-llvm already up-to-date
+    fi
+  '';
+
   meta = with lib; {
     description = "ROCm fork of the LLVM compiler infrastructure";
     homepage = "https://github.com/RadeonOpenCompute/llvm-project";