[LibFuzzer] Try to unbreak the `FuzzerMutate.ShuffleBytes1` unit test.

This test is failing on my Linux box. Just increasing the number of
iterations works around this. The divergence is likely due to
our reliance on `std::shuffle()` which is not guaranteed to have
the same behaviour across platforms.

This is a strong argument for us to implement our own shuffle
function to avoid divergence in behaviour across platforms.

Differential Revision: https://reviews.llvm.org/D45767

llvm-svn: 330390

compiler-rt/lib/fuzzer/tests/FuzzerUnittest.cpp

@@ -328,7 +328,7 @@ void TestShuffleBytes(Mutator M, int NumIter) {
 }
 
 TEST(FuzzerMutate, ShuffleBytes1) {
-  TestShuffleBytes(&MutationDispatcher::Mutate_ShuffleBytes, 1 << 16);
+  TestShuffleBytes(&MutationDispatcher::Mutate_ShuffleBytes, 1 << 17);
 }
 TEST(FuzzerMutate, ShuffleBytes2) {
   TestShuffleBytes(&MutationDispatcher::Mutate, 1 << 20);