Trim root path from output

When linkerconfig runs on host with --root argument, it prints root as
well like following:

$ linkerconfig --vndk R --root /tmp/test_root
...
namespace.foo.search_paths = /tmp/test_root/product/${LIB}
..

This change trims root from path variables and apex paths so the output
look more like real output.

Bug: n/a
Test: build/boot
      run linkerconfig on host and compare outputs

Change-Id: Icc91f297047f059684a42d825048e50e26873520
17 files changed