Merge "riscv64: stop reserving x18 for shadow call stack." am: 0ee012c2 am: 5823afea

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2534260



Change-Id: I95e512a3c407ba0a9c635d85dc9fd53b15897ad3
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>