When compiling the first time headunit-desktop sometimes gets stuck on the splash screen. Running
protoc --proto_path=modules/android-auto/headunit/hu/ --cpp_out=modules/android-auto/headunit/hu/generated.x64/ modules/android-auto/headunit/hu/hu.proto modules/android-auto/headunit/hu/bt.proto
mkdir build && cd build
qmake PREFIX=~/hud ../headunit-desktop.pro
make -j5
make install
again fixes this