make: fix BUILD_IN_DOCKER when RIOT is submodule

[smlng]

Contribution description

This removes a non-working mount point when using BUILD_IN_DOCKER for an
external application where RIOTBASE is a submodule within the apps repo.

Actually I'm not sure why the removed lines are in place anyway, because they are only used when RIOT is a submodule, however they likely never worked.

Testing procedure

Try to build an application with BUILD_IN_DOCKER=1 which has RIOT as a submodule within its repo and uses that as RIOTBASE. Take for instance this https://github.com/inetrg/vslab-riot and you'll get the following error:

cd /tmp
git clone https://github.com/inetrg/vslab-riot
cd vslab-riot
BUILD_IN_DOCKER=1 DOCKER="sudo docker" make -C src/
Launching build container using image "riot/riotbuild:latest".
sudo docker run --rm -t -u "$(id -u)" \
    -v '/tmp/vslab-riot/RIOT:/data/riotbuild/riotbase' \
    -v '/tmp/vslab-riot/RIOT/cpu:/data/riotbuild/riotcpu' \
    -v '/tmp/vslab-riot/RIOT/boards:/data/riotbuild/riotboard' \
    -v '/tmp/vslab-riot/RIOT/makefiles:/data/riotbuild/riotmake' \
    -v '/tmp/vslab-riot:/data/riotbuild/riotproject' \
    -v /etc/localtime:/etc/localtime:ro \
    -e 'RIOTBASE=/data/riotbuild/riotbase' \
    -e 'CCACHE_BASEDIR=/data/riotbuild/riotbase' \
    -e 'RIOTCPU=/data/riotbuild/riotcpu' \
    -e 'RIOTBOARD=/data/riotbuild/riotboard' \
    -e 'RIOTMAKE=/data/riotbuild/riotmake' \
    -e 'RIOTPROJECT=/data/riotbuild/riotproject' \
      -v src/.git:src/.git \
     \
    -w '/data/riotbuild/riotproject/src/' \
    'riot/riotbuild:latest' make
docker: Error response from daemon: invalid volume specification: 'src/.git:src/.git': invalid mount config for type "volume": invalid mount path: 'src/.git' mount path must be absolute.
See 'docker run --help'.
make: *** [..in-docker-container] Error 125

It works when you clone RIOT separately and specify RIOTBASE accordingly, e.g.

cd /tmp
git clone https://github.com/RIOT-OS/RIOT
cd /tmp/vslab-riot
RIOTBASE=/tmp/RIOT BUILD_IN_DOCKER=1 make -C src

Issues/PRs references

[jcarrano]

I could reproduce the problem, but this fix will break worktrees.

[jcarrano]

Removing this will break worktrees, which was fixed in #10303.

[jcarrano]

Here are the commands I used to reproduce the issue:

$ git clone git@github.com:inetrg/vslab-riot.git
$ cd vslab-riot
$ git submodule init
$ git submodule update
$ BUILD_IN_DOCKER=1 DOCKER="sudo docker" make -C src/
make: Entering directory '/home/jcarrano/source/vslab-riot/src'
Launching build container using image "riot/riotbuild:latest".
sudo docker run --rm -t -u "$(id -u)" \
    -v '/home/jcarrano/source/vslab-riot/RIOT:/data/riotbuild/riotbase' \
    -v '/home/jcarrano/source/vslab-riot/RIOT/cpu:/data/riotbuild/riotcpu' \
    -v '/home/jcarrano/source/vslab-riot/RIOT/boards:/data/riotbuild/riotboard' \
    -v '/home/jcarrano/source/vslab-riot/RIOT/makefiles:/data/riotbuild/riotmake' \
    -v '/home/jcarrano/source/vslab-riot:/data/riotbuild/riotproject' \
    -v /etc/localtime:/etc/localtime:ro \
    -e 'RIOTBASE=/data/riotbuild/riotbase' \
    -e 'CCACHE_BASEDIR=/data/riotbuild/riotbase' \
    -e 'RIOTCPU=/data/riotbuild/riotcpu' \
    -e 'RIOTBOARD=/data/riotbuild/riotboard' \
    -e 'RIOTMAKE=/data/riotbuild/riotmake' \
    -e 'RIOTPROJECT=/data/riotbuild/riotproject' \
    -v /home/jcarrano/.gitcache:/data/riotbuild/gitcache -e GIT_CACHE_DIR=/data/riotbuild/gitcache -v ../.git:../.git \
     \
    -w '/data/riotbuild/riotproject/src/' \
    'riot/riotbuild:latest' make  
docker: Error response from daemon: invalid volume specification: '../.git:../.git': invalid mount config for type "volume": invalid mount path: '../.git' mount path must be absolute.
See 'docker run --help'.
make: *** [/home/jcarrano/source/vslab-riot/RIOT/makefiles/docker.inc.mk:106: ..in-docker-container] Error 125
make: Leaving directory '/home/jcarrano/source/vslab-riot/src'

[cladmi]

Actually I'm not sure why the removed lines are in place anyway, because they are only used when RIOT is a submodule, however they likely never worked.

The description says worktree and not submodules.

You have more information in the commit introducing it 61a3e5d#diff-4417068c1754de9c0490bd66a2ea783e and also the detailed procedure in the PR introducing it #10303

[smlng]

changed as suggested by @jcarrano and it solves the problem for me, too!

[smlng]

@cladmi and @jcarrano can you have another look. I kind of need this (or at least its annoying) to use my PR branch for the RIOT submodule in a projects instead of the RIOT repo ...

[jcarrano]

Tested by using docker in with a submodule as in the description, and also verified that worktrees are still working.

[smlng]

🎉

[cladmi]

I prefered the old commit message though at least make: fix BUILD_IN_DOCKER when RIOT is submodule was explaining why it was changed. Now the title just says exactly what the code line does, so you need to dig into this PR to understand why it was modified.