Do not generate TEST_MAPPINGs for host tests

Instead of generating TEST_MAPPING entries for host tests, we add a
test_options section to its Android.bp entry.

Fixes: 176097100
Test: Manually run cargo2android on a few crates and verify the output
Change-Id: Ia57a53dad6910410c7e7aab6d592fba79720f998
1 file changed