Fixes [YOCTO #10692]
I updated the STAGING_DIR variable description to have a reference
to the SYSROOT_DIRS variable as well as the "Sharing Files
Between Recipes" section of the dev-manual.
I also updated the "Sharing Files Between Recipes" section so
that the role of SYSROOT_DIRS is explained and actually used
in an example to add another directory.
(From yocto-docs rev: 6539fcf632cfa3f076f874535ee9fc7ac291fbce)
Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>