scripts/contrib/build-perf-test.sh: skip network sanity tests

scripts/contrib/build-perf-test.sh: skip network sanity tests

When your proxy/network connection is unstable the network sanity test
which runs before every build (because we wipe all the files in the build dir)
can influence build time. Appending  CONNECTIVITY_CHECK_URIS = ""
in local.conf will disable the check.

(From OE-Core rev: cc1ed3c1940e4f64534b58de1b5fc6ef90362c9a)

Signed-off-by: Stefan Stanacar <stefanx.stanacar@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>