Merge "riscv64: typedef struct ucontext {...} ucontext_t." am: 61d435c29a

Original change: https://android-review.googlesource.com/c/platform/bionic/+/2515775

Change-Id: I6d5291f251d99861a11913f1b61d5a17729fa681
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>