Don't use a VLA for the double->string buffer.

Don't use a VLA for the double->string buffer.

Summary: MSVC is actually smarter about this than GCC, as MSVC doesn't support VLAs, it tries to eval the length at compile time. GCC on the other hand doesn't try to eval it at compile time, resulting in compiles via CMake telling us that this is a VLA.

Reviewed By: yfeldblum

Differential Revision: D2911929

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