You need to first set up the build directory by sourcing the poky build script,
after that builds can be run in that directory so long as bitbake is in $PATH
removing the need to source the init script for each build.
i.e:
$ . poky-init-build-env ~/my-build
$ bitbake some-image
<<later, in a different shell>>
$ cd ~/my-build
$ export PATH=/path/to/bitbake/bin:$PATH
$ bitbake an-image
This patch also removes use of OEROOT in recipes, etc.
