Setup Yocto

Double Open's layer, meta-doubleopen is used to create an SPDX Document describing the image built with Yocto. The layer needs to be added to conf/bblayers.conf and enabled with INHERIT += "doubleopen" in conf/local.conf.

After meta-doubleopen is added, bitbake build <RECIPE> produces SPDX Documents for all packages in <SPDX_DEPLOY_DIR> (defaults to /build/tmp/deploy/spdx/) and the SPDX Document for the whole image is saved to DEPLOY_DIR_IMAGE.