Added multiple operating system support in cmake buildscript. Main idea: all os-related code should be places in src/os/<os_name> folder with hierarchy used in src folder itself.
Added multiple operating system support in cmake buildscript. Main idea: all os-related code should be places in src/os/<os_name> folder with hierarchy used in src folder itself.

alexandrelucchesi/qlibc,kirbyfan64/qlibc,kirbyfan64/qlibc,alexandrelucchesi/qlibc,kirbyfan64/qlibc,alexandrelucchesi/qlibc