documentation/poky-ref-manual/ref-bitbake.xml: Updated BitBake Running a Task

I added more information about how BitBake actually runs a task.
The information has to do with how tightly BB controls the execution
environment of the build tasks to prevent contamination from the
build machine from leaking into the task execution environment.
This tight control actually causes some unexpected behavior during
builds.  For example, when a user exports and BB_ENV_EXTRAWHITE
an environment item such as CCACHE_DIR, the effects of the environment
item never make it to the BB task execution environment.  They only
make it to the data store.  The user actually has to take some extra
steps to export that environment item into the task execution environment.
The added information I put into the "Running a Task" section describes
these extra steps.

Fixes [YOCTO #689]
Reported-by: Wolfgang Denk <wd@denx.de>
(From yocto-docs rev: 182aa61693c2c7de8331569c30cbb8f41dad2315)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions