Tests: Fix RunCMake.try_compile CxxStandard case on MSVC
In post-3.9 development we've taught CMake to understand C++ language standards for MSVC. The RunCMake.try_compile test needs to know whether to expect support or not. Previously we depended on the host CMake version to know this, but CMake 3.9 and below do not. Add special logic to the test to account for this.
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