Fix the spawn test in the bypy environment

Required the launcher to be built since the pre-built
one was being used. Fixes #2881

kitty_tests/tui.py

@@ -3,13 +3,8 @@
 # License: GPL v3 Copyright: 2018, Kovid Goyal <kovid at kovidgoyal.net>
 
 
-import sys
-import unittest
-
 from . import BaseTest
 
-is32bit = sys.maxsize <= (1 << 32)
-
 
 class TestTUI(BaseTest):
 
@@ -48,7 +43,6 @@ class TestTUI(BaseTest):
         le.backspace()
         self.assertTrue(le.pending_bell)
 
-    @unittest.skipIf(is32bit, 'Fails for some unknown reason on 32bit builds')
     def test_multiprocessing_spawn(self):
         from kitty.multiprocessing import test_spawn
         test_spawn()