rust: Re-enable host address sanitizer.

Our toolchain supports a flag "-Z external-clangrt=true" which prevents
rustc from emitting a missing dependency to librust-dev_rt. Instead, we
link in libclang_rt.

Bug: 304507701
Bug: 324826914
Test: SANITIZE_HOST=address m aconfig
Change-Id: I8020c550b7a922c80620f61c22e01848a4f4a349