fix build.py on Windows

Author: DaanDeMeyer

build.py

@@ -2,8 +2,10 @@
 
 import subprocess
 import sys
+from os.path import join
 
 if __name__ == "__main__":
   OUT = 'out/cquery.vsix'
-  VSCE = 'node_modules/.bin/' + ('vsce.cmd' if sys.platform == 'win32' else 'vsce')
+  VSCE = 'vsce.cmd' if sys.platform == 'win32' else 'vsce'
+  VSCE = join('node_modules', '.bin', VSCE)
   sys.exit(subprocess.call([VSCE, 'package', '-o', OUT]))