feat(build): added support for build.lua, build/init.lua (#903)

lua/lazy/manage/task/plugin.lua

@@ -4,13 +4,23 @@ local Loader = require("lazy.core.loader")
 ---@type table<string, LazyTaskDef>
 local M = {}
 
+---@param plugin LazyPlugin
+local function get_build_file(plugin)
+  for _, path in ipairs({ "build.lua", "build/init.lua" }) do
+    path = plugin.dir .. "/" .. path
+    if Util.file_exists(path) then
+      return path
+    end
+  end
+end
+
 M.build = {
   ---@param opts? {force:boolean}
   skip = function(plugin, opts)
     if opts and opts.force then
       return false
     end
-    return not (plugin._.dirty and plugin.build)
+    return not (plugin._.dirty and (plugin.build or get_build_file(plugin)))
   end,
   run = function(self)
     vim.cmd([[silent! runtime plugin/rplugin.vim]])
@@ -18,6 +28,20 @@ M.build = {
     Loader.load(self.plugin, { task = "build" })
 
     local builders = self.plugin.build
+
+    local build_file = get_build_file(self.plugin)
+    if build_file then
+      if builders then
+        Util.warn(
+          ("Plugin **%s** provides its own build script.\nPlease remove the `build` option from the plugin's spec"):format(
+            self.plugin.name
+          )
+        )
+      end
+      builders = function()
+        Loader.source(build_file)
+      end
+    end
     if builders then
       builders = type(builders) == "table" and builders or { builders }
       ---@cast builders (string|fun(LazyPlugin))[]