This uses a fixed gcc version, 10.2, as that is what ardupilot is using, and seems to play along fine with glibc and gdbserver in blueos.
10.3 WILL NOT WORK IN BLUEOS
wget --no-clobber http://new.galvanicloop.com:8000/gcc-arm-10.2-2020.11-x86_64-arm-none-linux-gnueabihf.tar.xz
tar -xxvf gcc-arm-10.2-2020.11-x86_64-arm-none-linux-gnueabihf.tar.xz
git clone --recurse-submodules --branch Sub-4.1 https://github.com/ArduPilot/ardupilot.git