psmisc: Add ${S} to sed call to support separate build directory

:Release Notes:
Using ${B} != ${S} is safer for rebuilds in the same WORKDIR, fix
sed calls by using absolute path to ${S}.

:Detailed Notes:

:Testing Performed:
Only build tested.

:QA Notes:
No change to image.

:Issues Addressed:
[ANG-329] Ongoing metadata improvement/cleanup work

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>