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

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

Change-Id: I790425e4b15e2ee21ead0ca197d1963f711e1f6a