When use default install directory, we can't get the environment setup
script path. The reason is that opkg-cl list incorrect files paths.
This patch sets env_script variable to make us get correct environment
setup script path.
[YOCTO #6443]
(From OE-Core rev: e0080f279d5ebb320c2ba285765048fcca523fe7)
Signed-off-by: Chong Lu <Chong.Lu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>