[travis-ci] add supervisor mode qemu-riscv to the build
[travis-ci] add supervisor mode qemu-riscv to the build

littlekernel/lk,hollanderic/lkstuff,travisg/lk,hollanderic/lkstuff,hollanderic/lkstuff,littlekernel/lk,littlekernel/lk,travisg/lk,hollanderic/lkstuff,littlekernel/lk,travisg/lk,travisg/lk