TEST_MAPPING: add new test target to postsubmit am: aa24640479

Original change: https://android-review.googlesource.com/c/platform/external/llvm-libc/+/3487394

Change-Id: I841e184386d8d0c923bb624ca704969a0b7fd80b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>