[ASan] A speculative attempt to fix a flaky test on ppc64be.

[alekseyshl]

Summary

As mentioned in test/msan/fork.cc, if test output is redirected to a file
(as opposed to being piped directly to FileCheck), we may lose some "done"s due to
a kernel bug: https://lkml.org/lkml/2014/2/17/324, so let's pipe the
output of the test.

test/asan/TestCases/Posix/halt_on_error-torture.cc

 // Stress test recovery mode with many threads.
 //
 // RUN: %clangxx_asan -fsanitize-recover=address -pthread %s -o %t
 //
 // RUN: rm -f 1.txt
 // RUN: %env_asan_opts=halt_on_error=false:suppress_equal_pcs=false %run %t 1 10 >>1.txt 2>&1
 // RUN: FileCheck %s < 1.txt
 // RUN: grep 'ERROR: AddressSanitizer: use-after-poison' 1.txt | count 10
 // RUN: FileCheck --check-prefix=CHECK-NO-COLLISION %s < 1.txt
 //
 // Collisions are unlikely but still possible so we need the ||.
 // RUN: rm -f 10.txt
-// RUN: %env_asan_opts=halt_on_error=false:suppress_equal_pcs=false:exitcode=0 %run %t 10 20 >>10.txt 2>&1
+// RUN: %env_asan_opts=halt_on_error=false:suppress_equal_pcs=false:exitcode=0 %run %t 10 20 2>&1 | cat > 10.txt
 // RUN: FileCheck --check-prefix=CHECK-COLLISION %s < 10.txt || FileCheck --check-prefix=CHECK-NO-COLLISION %s < 10.txt
 //
 // Collisions are unlikely but still possible so we need the ||.
 // RUN: rm -f 20.txt
-// RUN: %env_asan_opts=halt_on_error=false:exitcode=0 %run %t 10 20 >>20.txt 2>&1
+// RUN: %env_asan_opts=halt_on_error=false:exitcode=0 %run %t 10 20 2>&1 | cat > 20.txt
 // RUN: FileCheck --check-prefix=CHECK-COLLISION %s < 20.txt || FileCheck --check-prefix=CHECK-NO-COLLISION %s < 20.txt
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <pthread.h>
 #include <time.h>
 
 #include <sanitizer/asan_interface.h>
 
 size_t nthreads = 10;
 size_t niter = 10;
 
 void random_delay(unsigned *seed) {
   *seed = 1664525 * *seed + 1013904223;
   struct timespec delay = { 0, (*seed % 1000) * 1000 };
   nanosleep(&delay, 0);
 }
 
 void *run(void *arg) {
   unsigned seed = (unsigned)(size_t)arg;
 
   volatile char tmp[2];
-  __asan_poison_memory_region(&tmp, sizeof(tmp)); 
+  __asan_poison_memory_region(&tmp, sizeof(tmp));
 
   for (size_t i = 0; i < niter; ++i) {
     random_delay(&seed);
     // Expect error collisions here
     // CHECK: ERROR: AddressSanitizer: use-after-poison
     volatile int idx = 0;
     tmp[idx] = 0;
   }