Add -Wno-unused-parameter to enable building for riscv64 am: 820ff0d95f am: 0bd6330fae am: bf2d9d7fc4 am: 938337bd99

Original change: https://android-review.googlesource.com/c/platform/external/pthreadpool/+/2663615

Change-Id: I9bd081a405367951ac4200c70321c5044ba4974e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>