`make acceptance` fails on casing on machinename

Describe the bug
Trying to make the source locally to test things out. Using WSL 2.0 on Windows 11 and the Makefile fails on the docker build command
https://github.com/actions-runner-controller/actions-runner-controller/blob/24602ff3ee05303e019b395b5d6805f2ebedaa14/Makefile#L109

With the error below, which makes sense.

docker build -t Rob-XPS9700:master-8c42f99d-dirty .
invalid argument "Rob-XPS9700:master-8c42f99d-dirty" for "-t, --tag" flag: invalid reference format: repository name must be lowercase
See 'docker build --help'.
make: *** [Makefile:109: docker-build] Error 125

Checks

• My actions-runner-controller version (v0.x.y) does support the feature
• I'm using an unreleased version of the controller I built from HEAD of the default branch

Solution
Make the label use a lowercase version of the machine name :-)

I was trying to do it, but I am very new to make. Normal lowercasing from bash isn't working ( ${NAME,,} )

Tried using the solution from here, but I cannot get that to work. Any help would be awesome :-)

Start at Makefile line 109 and reproduce the failure with make acceptance in the reported WSL environment. Check how the machine name is used in the Docker build tag; done means the generated tag is lowercase and the acceptance build completes successfully.