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/integral/c.inc

@@ -618,7 +618,7 @@ typedef uint64_t uintmax_t;
 #define textexit    _Section(".text.exit") noinstrument
 #define textreal    _Section(".text.real")
 #define textwindows _Section(".text.windows")
-#define textsyscall _Section(".text.syscall")
+#define textsyscall _Section(".text.syscall") noinline
 #define antiquity   _Section(".text.antiquity")
 #else
 #define testonly