prereq: SetupHostCommand: fix wrong check result

prereq: SetupHostCommand: fix wrong check result

Tony has reported, that CI tools job is failing for him in macOS
container due to prereq check failure for GNU `install` utility.

Michael diagnosed it and from his traces it was clear, that the issue is
caused by a wrong return value in the success check case, so lets fix it
accordingly.

Fixes: f75204036ccc ("prereq-build: allow host command symlinks to update")
Reported-by: Tony Ambardar <itugrok@yahoo.com>
Diagnosed-by: Michael Pratt <mcpratt@pm.me>
Signed-off-by: Petr Štetiar <ynezz@true.cz>