Export SOONG_HOST_OUT as ANDROID_SOONG_HOST_OUT

Some host tools (launch_cvd, etc.) have been using HOST_OUT.
As their dependencies are now installed by soong, the tools should refer
to SOONG_HOST_OUT. Export it as ANDROID_SOONG_HOST_OUT.

Bug: 172065015
Test: build aosp_cf_x86_phone, execute launch_cvd
Change-Id: Ie175049f15b89485feec0d33d82e756b12a7ad8a