[joltphysics] Disable treats all compiler warnings as errors

[LilyWangLL]

In an internal version of MSVC compiler, joltphysics install failed with following error:

D:\buildtrees\joltphysics\src\v2.0.1-76420d93c1.clean\Jolt\Core\Reference.h(115): error C2220: the following warning is treated as an error
D:\buildtrees\joltphysics\src\v2.0.1-76420d93c1.clean\Jolt\Core\Result.h(161): note: see reference to class template instantiation 'JPH::Ref<JPH::Shape>' being compiled
D:\buildtrees\joltphysics\src\v2.0.1-76420d93c1.clean\Jolt\Physics\Collision\Shape\Shape.h(137): note: see reference to class template instantiation 'JPH::Result<JPH::Ref<JPH::Shape>>' being compiled
D:\buildtrees\joltphysics\src\v2.0.1-76420d93c1.clean\Jolt\Core\Reference.h(115): warning C5266: 'const' qualifier on return type has no effect
D:\buildtrees\joltphysics\src\v2.0.1-76420d93c1.clean\Jolt\Core\Reference.h(115): note: to simplify migration, consider the temporary use of /Wv:18 flag with the version of the compiler with which you used to build without warnings

I have confirmed with developer, this change is by design and we need to disable this warning.

[BillyONeal]

In general we should be leaving the warnings in the output but just not failing the build over it.

Ideally the port would be fixed to not inject extra flags that it does not need like this too (so that what comes from the toolchain applies).

[BillyONeal]

Thanks!