Hi!
I was looking for a docker container to build blackmagic probe, found your project, but it does not work for me (I am building for stlink hardware). It appears that ubuntu builtin arm-gcc is not supported by BMP and in fact, even ARM GCC versions are not supported except one - 12.2.rel1. Different gcc versions produce output of different sizes and the resulting binary is not even guaranteed to work:
blackmagic-debug/blackmagic#1589 (comment)
blackmagic-debug/blackmagic#1579 (comment)

Here is a Dockerfile that I came up with (with the help of this file: https://github.com/hardwario/gcc-arm-embedded-docker/blob/master/Dockerfile)

FROM ubuntu:22.04

RUN mkdir /workdir && \
    apt-get update && \
    apt-get install -y make xz-utils wget git python3

RUN  wget -O archive.tar.xz "https://developer.arm.com/-/media/Files/downloads/gnu/12.2.rel1/binrel/arm-gnu-toolchain-12.2.rel1-x86_64-arm-none-eabi.tar.xz" && \
    tar xf archive.tar.xz -C /opt && \
    rm archive.tar.xz

ENV PATH=/opt/arm-gnu-toolchain-12.2.rel1-x86_64-arm-none-eabi/bin:$PATH

WORKDIR /workdir

From that, I ran

git clone https://github.com/blackmagic-debug/blackmagic.git --depth 1 --branch v1.10.2
cd blackmagic/
make PROBE_HOST=stlink ENABLE_RTT=1

I didn't put it into Dockerfile as I want to branch and make options to be configurable.