Deprecate ld.config.txt for fully treblelized devices

From latest change fully treblelized devices started to use
ld.config.txt from generator instead of the one under /system/etc. As so
existing ld.config.txt is no longer required. This change removes all
ld.config.txt content and build script for it.

Bug: 138920271
Test: m -j passed
Test: Tested from Cuttlefish
Change-Id: I9e2d4b305442a4fccc4378a997ec92bfd6cddb84