bootstrap: use 1.8.7-compatible #sub instead of 1.9.x-only #sub_ext
bootstrap: use 1.8.7-compatible #sub instead of 1.9.x-only #sub_ext

Signed-off-by: Wincent Colaiuta <c76ac2e9cd86441713c7dfae92c451f3e6d17fdc@wincent.com>

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent