Commit 90df2a955e3c ("defaultenv: Convert init script to C")
unintentionally changed the way the legacy "/env/bin/init" script is
run, so that it runs in a sub-shell context, effectively changing
`run_command("source /env/bin/init");` to
`run_command("/env/bin/init");`.  Therefore, any changes to shell
environment variables made by the script are undone when the script
exits.  This patch reverts back to the old behavior.

Fixes: 90df2a955e3c ("defaultenv: Convert init script to C")
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>