There's also a world beyond Unix. Prof. Bernstein may not be interested in targeting Windows. But for library developers in general, I'd recommend CMake. Microsoft has adopted CMake as its standard cross-platform C/C++ build system, and has built a cross-platform library package manager [1] on top of it.
As you see in the code this is linux only:
CLOCK_MONOTONIC, HW_CPUSPEED, -soname, -rpath, linux/perf_events.h,
Even on linux it would fail:
sort.c:386:21: error: always_inline function '_mm256_loadu_si256' requires target feature 'sse4.2', but would be inlined into function 'djbsort_int32' that is compiled without support for 'sse4.2'
[1]: https://github.com/Microsoft/vcpkg