DragonFlyBSD can be downloaded from the official page. After installation it should be configured for package repository. More information about package management is available here. Repository contains all required packages (GCC, Clang, CMake).

DragonFlyBSD can be run in QEMU, see an example command below:

qemu-system-x86_64 -m 2048 -M pc -smp cpus=2,sockets=1,cores=2,threads=1 \
  -drive if=none,media=cdrom,id=cd_main,readonly=on \
  -device ide-cd,bus=ide.0,drive=cd_main,bootindex=0 \
  -drive if=none,media=disk,id=main_hdd,file=dragonflybsd.qcow2 \
  -device ide-hd,bus=ide.1,drive=main_hdd,bootindex=1 \
  -nic user,model=rtl8139,hostfwd=tcp::10022-:22

You should not have any problems compiling with GCC.

Some newer Clang versions (e.g., 15.0.x) may crash when compiling the library, consider using the latest available version. Other than that, you should not have any problems compiling with Clang.