Extend the uint64 rank comparison trick (comparing [4]uint16 as a
single uint64) to arm64 builds. ARM64 is little-endian like x86, so
the same unsafe.Pointer cast produces correct lexicographic ordering.
This replaces a 4-iteration loop with a single uint64 comparison,
speeding up the sort phase.
Chromium file list, single-threaded:
linux: 126ms -> 126ms (sort not dominant)
src: 462ms -> 438ms (-5%, sort-heavy)
Junegunn Choi
6087055305