/postinstall/* does not search for a lib in /vendor or /odm

There has been no section in the linker config file for the binaries
under /postinstall. As a result, the binaries were run with the legacy
default config where /vendor/lib and /odm/lib are added to the search
paths. This is causing selinux denials as the binaries for OTA are not
allowed to access /vendor/lib or /odm/lib, but the dynamic linker calls
realpath(3) on the paths to canonicalize them.

Fixing the issue by letting /postinstall/* binaries to run with a
dedicated linker namespace config, where /vendor/lib and /odm/lib are
not added to the search paths. Not having the paths is okay because
he OTA binaries should not have dependency to the libs there.

Bug: 75287236
Test: do the OTA, selinux denials on postinstall_file is not shown
Test: above test should pass on  wahoo, marlin and pre-treble devices
Change-Id: I49c11a0929002adfef667890c0a375c2b41054f4