Pass CMAKE_GENERATOR_PLATFORM to third-party build if set
Pass CMAKE_GENERATOR_PLATFORM to third-party build if set

Thanks for Isaiah Norton <ihnorton@users.noreply.github.com>'s initial commit.

cedral/aws-sdk-cpp,awslabs/aws-sdk-cpp,jt70471/aws-sdk-cpp,jt70471/aws-sdk-cpp,cedral/aws-sdk-cpp,aws/aws-sdk-cpp,awslabs/aws-sdk-cpp,jt70471/aws-sdk-cpp,awslabs/aws-sdk-cpp,aws/aws-sdk-cpp,cedral/aws-sdk-cpp,jt70471/aws-sdk-cpp,aws/aws-sdk-cpp,cedral/aws-sdk-cpp,aws/aws-sdk-cpp,aws/aws-sdk-cpp,jt70471/aws-sdk-cpp,cedral/aws-sdk-cpp,jt70471/aws-sdk-cpp,cedral/aws-sdk-cpp,awslabs/aws-sdk-cpp,aws/aws-sdk-cpp