Fixes warnings like:
```
dolphin/Source/UnitTests/Common/BitUtilsTest.cpp:5:
../Externals/gtest/googletest/include/gtest/gtest.h:1392:11: warning: comparison of integers of different signs: 'const unsigned long' and 'const int' [-Wsign-compare]
if (lhs == rhs) {
~~~ ^ ~~~
../Externals/gtest/googletest/include/gtest/gtest.h:1421:12: note: in instantiation of function template specialization 'testing::internal::CmpHelperEQ<unsigned long, int>' requested here
return CmpHelperEQ(lhs_expression, rhs_expression, lhs, rhs);
^
dolphin/Source/UnitTests/Common/BitUtilsTest.cpp:12:3: note: in instantiation of function template specialization 'testing::internal::EqHelper<false>::Compare<unsigned long, int>' requested here
EXPECT_EQ(Common::BitSize<s8>(), 8);
^
../Externals/gtest/googletest/include/gtest/gtest.h:1924:63: note: expanded from macro 'EXPECT_EQ'
EqHelper<GTEST_IS_NULL_LITERAL_(val1)>::Compare, \
```
9234ed82da