Fix mismatched user and group ownership in Docker script.

[TheScarFr]

https://discord.com/channels/282045216221822978/282046743338811392/1424555618668384339 up to https://discord.com/channels/282045216221822978/282046743338811392/1424583169750863902 .

Prad wrote:

Only thing I remember having had to change there (both on Windows 7 Docker-Toolbox and Ubuntu 20.04 Docker) was replace chown -R dirtsand /opt/dirtsand with chown -R dirtsand:dirtsand /opt/dirtsand ... the script is executed as root user inside the container, but chown dirtsand <filepath> only changes the user, not the group the user is in, so you end up with files belonging to dirtsand:root which the user dirtsand:dirtsand (defined as USER dirtsand in line 83) doesn't have access to ... I had to delete the erratic containers and re-build dockersand with the modified DockerFile (running the bat file again with build as argument) ...

Prad wrote:

AH, and I had to change cmake --build string_theory/build --parallel into cmake --build string_theory/build --parallel 1 as well as cmake --build dirtsand/build --parallel into cmake --build dirtsand/build --parallel 1 ... for some reason multithreaded builds of dockersand never worked well for me (neither on windows 7 with docker-toolbox nor on ubuntu 20.04 with docker) ... I don't really know why alpine Linux is really struggling with multithreaded builds of programs on sufficiently modern machines) ...

The Desktop computer I installed dirtsand on, run Windows 11 Pro x64, and I had an issue that disallowed me to build dockersand; the fix proposed by Prad worked for me too.