PATH=x command -v uses original PATH instead of x

[Hello71]

https://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_09_01

[emersion]

This applies to all builtins in general.

[Hello71]

took a look at https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html, I think some other builtins affected (probably not exhaustive):

LC_MESSAGES=x anything-with-output
IFS=x read
HOME=x cd