Eliminate some flakes

- Get ASAN working on Windows.

- Deleting directories and then recreating them with the same name in a
  short period of time appears to be a no-no on Windows.

- There's no reason to call FlushFileBuffers on close() for pipes, and
  it's harmful since it might block indefinitely for no good reason.

libc/runtime/findmemoryinterval.c

@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/runtime/memtrack.h"
 
-unsigned FindMemoryInterval(const struct MemoryIntervals *mm, int x) {
+noasan unsigned FindMemoryInterval(const struct MemoryIntervals *mm, int x) {
   unsigned l, m, r;
   l = 0;
   r = mm->i;