toolchain-scripts-base: add base class for toolchain_create_sdk_version
We use toolchain_create_sdk_version() in buildtools-tarball but
don't want the extra classes toolchain-scripts pulls in, therefore
split out a separate base class for this function which both
toolchain-scripts and the buildtools-tarball can inherit.
Signed-off-by: Joshua Lock <joshua.g.lock@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
