Fix incorrect soong symlink rule

Soong was incorrectly creating symlinks by not making the link target
relative to the link location. This caused symlink_prefered_arch to
not work when run with --skip-make.

Test: ALLOW_MISSING_DEPENDENCIES=true OUT_DIR=out DIST_DIR=out/dist \
      ./art/tools/dist_linux_bionic.sh -j80 com.android.runtime.host dex2oatd
      ls -l out/host/linux_bionic-x86/bin

Change-Id: I0ae5f059d19c0eec53e4d7c8dc68ae890980e6b4