Include tools/files for GSI artifacts

Tools/files added in this CL are necessary for mixing GSI with vendor
images from other product and for the GSI to run on the emulator.

Bug: 136786169
Test: $ lunch aosp_x86-userdebug
      $ m -j updatepackage otatools-package emu_extra_imgs
      $ cd $TMP_DIR
      $ unzip $OUT/emu-extra-linux-system-images-eng.ycchen.zip
      $ cd x86
      $ unzip -n $OUT/aosp_x86-img-eng.ycchen.zip
      $ unzip $OUT/otatools bin/mk_combined_img bin/sgdisk
      $ unzip $OUT/otatools lib64/libc++.so lib64/libext2_uuid-host.so
      $ cut -d/ -f5 system-qemu-config.txt > composit.txt
      $ SGDISK=bin/sgdisk bin/mk_combined_img -i composit.txt -o system.img
      $ cd ..
      # Download sdk-repo-linux-emulator-*.zip from AB
      $ unzip -l sdk-repo-linux-emulator-*.zip
      $ ANDROID_PRODUCT_OUT=x86 ANDROID_BUILD_TOP=x86 emulator/emulator

Change-Id: Ibf88652eb4fb3244553062bbfb8bceac9a5cda47