Merge "Switch to musl memmem (via OpenBSD)." am: 422b2044ea am: f17844764d am: 4ea8b3d064 am: 3d48de5b05

Original change: https://android-review.googlesource.com/c/platform/bionic/+/1393677

Change-Id: I4a99226b84792d5179e629eea6eb41adf1c95e3d