ls, tar: Guard inclusion of sys/sysmacros.h by absence of major definition

Since musl 1.1.23, it too does not provide `major` and `minor` through
sys/types.h, so instead include sys/sysmacros.h based on the absence of
`major` rather than only on glibc.

Thanks to Rich Felker for the suggestion.

tar.c

@@ -2,7 +2,7 @@
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
-#ifdef __GLIBC__
+#ifndef major
 #include <sys/sysmacros.h>
 #endif