Dont sort on mtime

Files are built in order by size anyway and mtime sort makes link order
mtime dependent which breaks reproducible builds on openSUSE as they
modify mtimes randomnly. See #1804

setup.py

@@ -528,9 +528,6 @@ def find_c_files():
             ans.append(os.path.join('kitty', x))
         elif ext == '.h':
             headers.append(os.path.join('kitty', x))
-    ans.sort(
-        key=lambda x: os.path.getmtime(x), reverse=True
-    )
     ans.append('kitty/parser_dump.c')
     return tuple(ans), tuple(headers)