You can use the following script in your build file:

-------

kpse.set_program_name "luatex"
local lg_file = arg[1]
-- list of removed extensions
local patterns = arg[2] or "html,css"

if not lg_file then
print "No input file"
os.exit()
end

lg_file = lg_file:gsub("tex$","lg")
if not lg_file:match "lg$" then
lg_file = lg_file ..".lg"
end

local removed_extensions = {}
for ext in patterns:gmatch("([^,]+)") do
removed_extensions[ext] = true
end

function file_exists(name)
local f=io.open(name,"r")
if f~=nil then io.close(f) return true else return false end
end

local current_dir = lfs.currentdir()
local remove = function(filename)
local removed = current_dir .."/" .. filename
if file_exists(removed) then
print("Removing", removed)
os.remove(removed)
end
end

local files = {}
local images = {}

local file_pattern = "File: (.*)"
local image_pattern = "--- needs --- .-==> ([^%s]+) ---"

for line in io.lines(lg_file) do
local file_match = line:match(file_pattern)
local image_match = line:match(image_pattern)
files[#files + 1] = file_match
images[#images + 1] = image_match
end

for _, v in ipairs(files) do
local ext = v:match "([^%.]+)$"
if removed_extensions[ext] then
remove(v)
end
end
for _,v in ipairs(images) do
remove(v)
end

------

you can call it with command

texlua removefiles.lua texfilename "listofremovedextensions"

list of removed extensions isn't necessary, it removes html and css files by default. and of course images generated from the DVI file.