site/common: deactivate a runtime check for ipv6-support in python >=2.7.1 that fails when cross-compiling

In configure there is a runtime check to determine buggy getaddrinfo and as we
are cross-compiling this check goes wrong. If ipv6 is enabled in python, the
failed test is reported as fatal error with the message
Fatal: You must get working getaddrinfo() function.

Setting ac_cv_buggy_getaddrinfo=no deactivates the runtime check and allows to
compile python with ipv6 enabled.

This commit was derived from the commit 700b75e7661062aa93cf81205b78c8bf7609922d
in the Classic OpenEmbedded Development Tree.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@oss.bmw-carit.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>