<any>: std::any links when exceptions are disabled

[fsb4000]

Fixes #990

[StephanTLavavej]

After looking at this, I agree that the change is correct and ABI-safe.

Usually, anything mentioning _CRTIMP2_IMPORT affects ABI. However, your analysis is correct - these are guarded by #if !_HAS_EXCEPTIONS and we never build the STL's DLL in that mode (with the exception of stl/src/raisehan.cpp but that doesn't drag in <typeinfo>), so they never expand to __declspec(dllexport). Thus the macros should be removed, so that they never expand to __declspec(dllimport) for user code.

I have verified this by inspecting the DLL's exports (these types don't appear), and by performing an internal build of the STL with

#if !_HAS_EXCEPTIONS

#if defined(CRTDLL2) && defined(_CRTBLD)
#error WOOF
#endif

// ...

here; it succeeded, proving that these are indeed never exported.

[StephanTLavavej]

I'm (speculatively) mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

[StephanTLavavej]

Thanks for fixing this long-standing bug! 😻 🐞 🎉