[cmake] Windows check ARM64/WIN64 symbols #51
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Similar issues as Pulse-Eight/libcec#675
the
_M_ARM64symbol isnt available always at cmake configure time.Instead use check_symbol_exists to be able to test for Arch specific symbols for x64 and arm64 arch types correctly always.
Also, add removal of /arch:SSE2 flag for arm64 arch type as well to remove warnings.