Silence a warning:

In file included from ../unittests/Support/ProcessTest.cpp:11:
../utils/unittest/googletest/include/gtest/gtest.h:1448:28: warning: comparison of integers of different signs: 'const unsigned int' and 'const int' [-Wsign-compare]
GTEST_IMPL_CMP_HELPER_(NE, !=);
~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
../utils/unittest/googletest/include/gtest/gtest.h:1433:12: note: expanded from macro 'GTEST_IMPL_CMP_HELPER_'
  if (val1 op val2) {\
           ^
../unittests/Support/ProcessTest.cpp:46:3: note: in instantiation of function template specialization 'testing::internal::CmpHelperNE<unsigned int, int>' requested here
  EXPECT_NE((r1 | r2), 0);
  ^