Remove -DIGC_OPTION__ARCHITECTURE_TARGET build option

[dvrogozh]

Please, remove -DIGC_OPTION__ARCHITECTURE_TARGET build option. It is useless: cmake provides other ways to detect your architecture target. If you just need to check bitness:

if(CMAKE_SIZEOF_VOID_P EQUAL 8)
    message("architecture: 64-bit")
else()
    message("architecture: 32-bit")
endif()

If you need to check Linux/Windows/etc., review: https://cmake.org/Wiki/CMake_Cross_Compiling

[dvrogozh]

@chivakker : FYI

[iwwu]

Thank you for the suggestion. Work in progress

[iwwu]

Request completed. Please use latest code or tag 'igc_release_2018-12-12'. README is updated as well.

[iwwu]

Closing the issue since the fix is already merged.

[dvrogozh]

works for me. thank you.