Trying to build QEMU on sparc64 fails with:
[4648/8435] c++ -o qemu-system-ppc64 qemu-system-ppc64.p/softmmu_main.c.o libcommon.fa.p/ui_vnc-auth-sasl.c.o libcommon.fa.p/migration_colo-failover.c.o libcommon.fa.p/hw_input_vhost-user-input.c.o libcommon.fa.p/replay_replay-random.c.o libcommon.fa.p/hw_9pfs_codir.c.o libcommon.fa.p/hw_display_edid-region.c.o libcommon.fa.p/hw_net_vhost_net.c.o libcommon.fa.p/hw_isa_i82378.c.o libcommon.fa.p/backends_rng-egd.c.o libcommon.fa.p/hw_usb_core.c.o libcommon.fa.p/hw_pci-bridge_i82801b11.c.o libcommon.fa.p/net_tap.c.o libcommon.fa.p/hw_ipack_ipack.c.o libcommon.fa.p/hw_scsi_mptconfig.c.o libcommon.fa.p/hw_usb_libhw.c.o libcommon.fa.p/hw_display_sm501.c.o libcommon.fa.p/hw_net_rocker_rocker_world.c.o libcommon.fa.p/fsdev_qemu-fsdev.c.o libcommon.fa.p/backends_tpm_tpm_util.c.o libcommon.fa.p/net_tap-linux.c.o libcommon.fa.p/hw_net_rocker_rocker_fp.c.o libcommon.fa.p/hw_usb_dev-uas.c.o libcommon.fa.p/hw_net_fsl_etsec_miim.c.o libcommon.fa.p/net_queue.c.o libcommon.fa.p/hw_isa_isa-superio.c.o libcommon.fa.p/migration_global_state.c.o libcommon.fa.p/backends_rng-random.c.o libcommon.fa.p/hw_ipmi_ipmi_bmc_extern.c.o libcommon.fa.p/migration_postcopy-ram.c.o libcommon.fa.p/hw_scsi_megasas.c.o libcommon.fa.p/hw_acpi_acpi-stub.c.o libcommon.fa.p/hw_nvram_mac_nvram.c.o libcommon.fa.p/hw_net_pcnet-pci.c.o libcommon.fa.p/cpus-common.c.o libcommon.fa.p/hw_core_qdev-properties-system.c.o libcommon.fa.p/migration_colo.c.o libcommon.fa.p/ui_spice-module.c.o libcommon.fa.p/hw_usb_hcd-ehci-pci.c.o libcommon.fa.p/migration_exec.c.o libcommon.fa.p/hw_input_adb-kbd.c.o libcommon.fa.p/hw_timer_xilinx_timer.c.o libcommon.fa.p/hw_cpu_core.c.o libcommon.fa.p/chardev_msmouse.c.o libcommon.fa.p/migration_socket.c.o libcommon.fa.p/hw_9pfs_9p-synth.c.o libcommon.fa.p/backends_dbus-vmstate.c.o libcommon.fa.p/net_colo-compare.c.o libcommon.fa.p/hw_misc_macio_cuda.c.o libcommon.fa.p/hw_audio_intel-hda.c.o libcommon.fa.p/audio_audio_legacy.c.o
(...)
libio.fa libchardev.fa -Wl,--no-whole-archive -Wl,--warn-common -Wl,-z,relro -Wl,-z,now -m64 -g -O2 -fdebug-prefix-map=/<<PKGBUILDDIR>>=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -Wl,-z,relro -Wl,--as-needed -fstack-protector-strong libmigration.fa -Wl,--start-group libqemuutil.a contrib/libvhost-user/libvhost-user.a libqmp.fa libhwcore.fa libblockdev.fa libblock.fa libcrypto.fa libauthz.fa libqom.fa libio.fa libchardev.fa @block.syms @qemu.syms /usr/lib/gcc/sparc64-linux-gnu/10/../../../sparc64-linux-gnu/libfdt.so /usr/lib/sparc64-linux-gnu/libcapstone.so -lepoxy -lgbm /usr/lib/sparc64-linux-gnu/libpixman-1.so /usr/lib/sparc64-linux-gnu/libz.so /usr/lib/sparc64-linux-gnu/libslirp.so /usr/lib/sparc64-linux-gnu/libglib-2.0.so -lrdmacm -libverbs -libumad -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0 /usr/lib/gcc/sparc64-linux-gnu/10/../../../sparc64-linux-gnu/libsasl2.so @block.syms -lusb-1.0 /lib/sparc64-linux-gnu/libudev.so /usr/lib/sparc64-linux-gnu/libpng16.so -lvdeplug /usr/lib/sparc64-linux-gnu/libjpeg.so -pthread -luring -lgnutls -lutil -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0 -lm -Wl,--export-dynamic -lgmodule-2.0 -lglib-2.0 -laio -luring -lgnutls -lnettle -lstdc++ -Wl,--end-group
/usr/bin/ld: libqemu-ppc64-softmmu.fa.p/hw_ppc_spapr_hcall.c.o: in function `h_update_dt':
./b/qemu/../../hw/ppc/spapr_hcall.c:1966: undefined reference to `fdt_check_full'
collect2: error: ld returned 1 exit status
Full build log available at: https://buildd.debian.org/status/fetch.php?pkg=qemu&arch=sparc64&ver=1%3A5.2%2Bdfsg-1&stamp=1607502300&raw=0
Looking at the build log, it seems like your system libfdt is version 1.4.6.
However, that fdt_check_full function is only properly available with
version >= 1.5.1, if I get that right.
As a workaround, you could try to run the configure script with
--enable-fdt=git (or of course update your system version to 1.5.1 if
somehow possible).