An example of how you could use Premake for your asset building pipeline.

premake-asset-pipeline.lua

newaction {
	trigger = "assets",
	description = "Build game assets",

	execute = function()

		local assetSourcePaths = os.matchfiles("assets/source/**")
		local assetBuiltPaths = os.matchfiles("assets/built/**")

		removeJunkFiles(assetSourcePaths)
		removeJunkFiles(assetBuiltPaths)

		local filesToMirror = {}
		local generatorPaths = {}

		-- gather the files
		for i, path in ipairs(assetSourcePaths) do
			if path:endswith("generator.lua") then
				table.insert(generatorPaths, path)
			elseif not path:endswithanyof({".prog", ".vert", ".frag", ".blend", ".blend1"}) then
				table.insert(filesToMirror, path)
			end
		end

		local generators = loadGenerators(generatorPaths)
		local generatorOutputs = {}

		-- build a list of generator outputs
		for _,generator in ipairs(generators) do
			for _,rule in ipairs(generator.rules) do
				for _,output in ipairs(rule.outputs) do
					table.insert(generatorOutputs, output)
				end
			end
		end

		print("\n# Cleaning Built Assets Folder")

		-- delete orphaned assets from the built folder
		for i,built in ipairs(assetBuiltPaths) do
			local src = built:gsub("assets/built", "assets/source")
			if not table.contains(filesToMirror, src) and -- file is to be mirrored
				not table.contains(generatorOutputs, built) -- file is a generated output
			then
				print("removing", built)
				if not os.remove(built) then
					printError("ERROR: failed to remove file: "..built)
				end
			end
		end

		print("\n# Copying Assets")

		copyModifiedFiles(filesToMirror)

		print("\n# Running Generators")

		executeGenerators(generators)

		print("\n# Done Building Assets")
	end
}