add qemu to the docker image

3 jobs for master in 1 minute and 24 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Prepare
passed prepare:docker #1747852
docker

00:00:40

 
  Build
failed build:loader #1747853

00:00:43

 
  Deploy
skipped deploy:loader #1747854
docker
 
Name Stage Failure
failed
build:loader Build
  Downloaded dtoa v0.4.6
Downloaded bit_field v0.10.0
Downloaded multiboot v0.3.0
Downloaded x86 v0.34.0
error: "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/Cargo.lock" does not exist, unable to build with the standard library, try:
rustup component add rust-src
make: *** [Makefile:46: loader] Error 101
Cleaning up file based variables
ERROR: Job failed: command terminated with exit code 1