The Rust toolchain only supports Linux hosts, so skip Rust tests
that depend on host toolchains when building on other platforms.
Test: Tests still run on Linux hosts
Bug: 140435149
Change-Id: I298b52589ab5c6a7ec3acc4db1111596cd995d76
Adds support to Soong for building rust modules. This currently only
supports x86_64 device and x86 linux host targets. The functionality
is sufficient to build crosvm.
Bug: 136189233
Test: Test module builds.
Test: crosvm builds.
Change-Id: I6ea04615834a6d673578ab10ea1a2eb04259fe09