USER command set wrong $HOME or gid

[qwazerty]

Actual behavior
Switching to a different user does not do the same behavior on $HOME and gid as the native docker build commands.

Expected behavior
When using USER runner, the gid and groups should be set to uid=1000(runner) gid=1000(runner) groups=1000(runner).
When using USER runner:runner the $HOME should be set to /home/runner.

To Reproduce
Using this Dockerfile produce the following output.

FROM ubuntu:latest

RUN useradd -m -s /bin/bash runner
USER runner
RUN echo $HOME; id
USER runner:runner
RUN echo $HOME; id

With kaniko (keeping just enough log)

$ /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile --destination repository.../$CI_PROJECT_NAME:latest
INFO[0000] Downloading base image ubuntu:latest
INFO[0005] RUN useradd -m -s /bin/bash runner
INFO[0005] USER runner
INFO[0005] RUN echo $HOME; id
/home/runner
uid=1000(runner) gid=0(root) groups=0(root)        <-- Wrong gid and groups
INFO[0006] USER runner:runner
INFO[0006] RUN echo $HOME; id
/                                                  <-- Wrong $HOME
uid=1000(runner) gid=1000(runner) groups=1000(runner)

With docker build.

Step 1/6 : FROM ubuntu:latest
latest: Pulling from library/ubuntu
Step 2/6 : RUN useradd -m -s /bin/bash runner
Step 3/6 : USER runner
Step 4/6 : RUN echo $HOME; id
/home/runner
uid=1000(runner) gid=1000(runner) groups=1000(runner)
Step 5/6 : USER runner:runner
Step 6/6 : RUN echo $HOME; id
/home/runner
uid=1000(runner) gid=1000(runner) groups=1000(runner)

[cvgw]

I imagine this issue is related to #822