Merge "Trivial strxfrm coverage improvement." am: 6900a09fe7 am: 1caae5f7f5 am: b0cef76f70

Original change: https://android-review.googlesource.com/c/platform/bionic/+/1393618

Change-Id: I1772a7fe56bcd3923242063a3137a5c69734ab4d