Avoid `-target riscv64-linux-androidVanillaIceCream`.

clang silently ignores such things rather than reporting them as errors.

With this change, verbose.log.gz says android10000 instead, as expected.

Bug: https://buganizer.corp.google.com/issues/315788463#comment24
Test: treehugger
Change-Id: I0d92b0747912f28065de0d2dc6b4d33d1c2c9857