Fixed build with GCC 11 by moving MSVC flags

[xvitaly]

Fixed build with GCC 11 by moving MSVC flags:

-- Performing Test C_FLAG_sdl
-- Performing Test C_FLAG_sdl - Failed
-- Performing Test C_FLAG_fstack_protector_strong
-- Performing Test C_FLAG_fstack_protector_strong - Failed
-- Performing Test C_FLAG_msse2
-- Performing Test C_FLAG_msse2 - Failed
-- Performing Test C_FLAG_mssse3
-- Performing Test C_FLAG_mssse3 - Failed
-- Performing Test C_FLAG_msse4_1
-- Performing Test C_FLAG_msse4_1 - Failed
-- Performing Test C_FLAG_mavx2
-- Performing Test C_FLAG_mavx2 - Failed
gcc: warning: /GS: linker input file unused because linking not done

Closes #132.

[Vascom]

I appied patch. Built succesfull.

[tianjunwork]

Thank you @xvitaly for the contribution.