fstatat64 is macrod to fstatat in sys/stat.h in musl- but then that fstatat is
used in the _syscall4 macro mapping to __NR_$name, and __NR_fstatat is not
defined anywhere here, as it wants the 64 name.

so, just let it keep the name with an undef of the stat.h macro, then the macro
expansion below evaluates correctly.
--- a/third_party/lss/linux_syscall_support.h
+++ b/third_party/lss/linux_syscall_support.h
@@ -4947,7 +4947,8 @@
   # endif
   #endif
   #if defined(__NR_fstatat64)
+    #undef fstatat64
     LSS_INLINE _syscall4(int,   fstatat64,        int,   d,
                          const char *,      p,
                          struct kernel_stat64 *,   b,    int,   f)
   #endif