DRM.cpp needs more than 8 MiB of compiler stack. GCC raises its own limit natively, but the aarch64 builder runs under QEMU user-mode emulation, which fixes the guest stack at exec and ignores setrlimit, so cc1plus segfaulted. Unpatched 0.15.1 fails the same way. QEMU_STACK_SIZE sizes it at exec; native builds ignore it and the object code is identical.