env: currently tries to parse too many arguments #7750
Description
$ env echo gotcha -u=kQ4dALb1 A=0d CZj=lYr
gotcha -u=kQ4dALb1 A=0d CZj=lYr
$ cargo run -q env echo gotcha -u=kQ4dALb1 A=0d CZj=lYr
env: cannot unset '=kQ4dALb1': Invalid argument
[$? = 125]
$ env -i -- -u=kQ4dALb1 A=0d CZj=lYr
-u=kQ4dALb1
A=0d
CZj=lYr
$ cargo run -q env -i -- -u=kQ4dALb1 A=0d CZj=lYr
env: cannot unset '=kQ4dALb1': Invalid argument
[$? = 125]Recovered from #6172, which tried to add a test for this (but didn't fix it).