Add toolchain/xz to build-tools

So that we can build xz, and use that one instead of a random one that
may or may not be installed on the host system.

Bug: 36130900
Test: build xz on darwin and linux
1 file changed
tree: 8d8b67ddbbd86381ad9903c6a8befd2a30ba96c9
  1. default.xml