build: update to use go1.12rc1 for the build
build: update to use go1.12rc1 for the build

ncw/rclone,ncw/rclone,olihey/rclone,olihey/rclone,ncw/rclone,B4dM4n/rclone,B4dM4n/rclone,olihey/rclone,ncw/rclone,B4dM4n/rclone,olihey/rclone,B4dM4n/rclone