Disable VS warning C4307

When building with VS2017, the build currently fails with :

> ./test/hotspot/gtest/utilities/test_align.cpp(96): error C2220: warning treated as error - no 'object' file generated
> ./test/hotspot/gtest/utilities/test_align.cpp(156): note: see reference to function template instantiation 'void static_test_alignments<T,A>(void)' being compiled
> with
> [
> T=int64_t,
> A=uint8_t
> ]
> ./test/hotspot/gtest/utilities/test_align.cpp(162): note: see reference to function template instantiation 'void test_alignments<int64_t,uint8_t>(void)' being compiled
> ./test/hotspot/gtest/utilities/test_align.cpp(96): warning C4307: '+': integral constant overflow
>
>

This might be related to an issue fixed at least in some versions of VS2019 , that is discussed here :

https://developercommunity.visualstudio.com/content/problem/211134/unsigned-integer-overflows-in-constexpr-functionsa.html

This problem has already come up elsewhere, see : 8253089: Windows (MSVC 2017) build fails after JDK-8243208
So it might be a good idea to disable the warning .