layer.conf: fix sanity error for PATH variable in extensible SDK workflow
Sanity checker reports following error for the PATH variable,
when bitbake -e <recipe> command is run in an extensible SDK workspace.
PATH contains '.', './' or '' (empty element), which will break the build
In case of extensible SDK, PATH variable is formed with two consecutive ':'
as bb.utils.which(d.getVar('PATH'),'bitbake') call returns an empty string.
This change adds ':' if BITBAKEPATH is a non empty string.
Signed-off-by: Sourabh Banerjee <sbanerje@codeaurora.org> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
