Builds OK with gcc-9 on Ubuntu bionic:

/bin/bash ../libtool  --tag=CC   --mode=link gcc-9  -g -O2 -lm -lbsd `pkg-config --libs glib-2.0 gio-2.0`  -o fwts fwts-main.o acpi/ac_adapter/fwts-ac_adapter.o acpi/acpidump/fwts-acpidump.o acpi/acpiinfo/fwts-acpiinfo.o acpi/acpitables/fwts-acpitables.o sbbr/acpitables/fwts-acpitables.o acpi/apicinstance/fwts-apicinstance.o acpi/asf/fwts-asf.o acpi/aspt/fwts-aspt.o acpi/battery/fwts-battery.o acpi/bert/fwts-bert.o acpi/bgrt/fwts-bgrt.o acpi/boot/fwts-boot.o acpi/brightness/fwts-brightness-helper.o acpi/brightness/fwts-brightness.o acpi/brightness/fwts-autobrightness.o acpi/checksum/fwts-checksum.o acpi/cpep/fwts-cpep.o acpi/crsdump/fwts-crsdump.o acpi/crsdump/fwts-prsdump.o acpi/csrt/fwts-csrt.o acpi/cstates/fwts-cstates.o acpi/dbgp/fwts-dbgp.o acpi/dbg2/fwts-dbg2.o acpi/devices/ac_adapter/fwts-ac.o acpi/devices/battery/fwts-battery.o acpi/devices/battery/fwts-smart_battery.o acpi/devices/ec/fwts-ec.o acpi/devices/buttons/fwts-power_button.o acpi/devices/buttons/fwts-sleep_button.o acpi/devices/lid/fwts-lid.o acpi/devices/sensor/fwts-als.o acpi/devices/time/fwts-time.o acpi/devices/wpc/fwts-wpc.o acpi/dmar/fwts-dmar.o acpi/dppt/fwts-dppt.o acpi/drtm/fwts-drtm.o acpi/dsddump/fwts-dsddump.o acpi/ecdt/fwts-ecdt.o acpi/einj/fwts-einj.o acpi/erst/fwts-erst.o acpi/facs/fwts-facs.o acpi/fadt/fwts-fadt.o sbbr/fadt/fwts-fadt.o acpi/fan/fwts-fan.o acpi/fpdt/fwts-fpdt.o acpi/gpedump/fwts-gpedump.o acpi/gtdt/fwts-gtdt.o acpi/hest/fwts-hest.o acpi/hpet/fwts-hpet.o acpi/hmat/fwts-hmat.o acpi/iort/fwts-iort.o acpi/lid/fwts-lid.o acpi/lpit/fwts-lpit.o acpi/madt/fwts-madt.o acpi/mcfg/fwts-mcfg.o acpi/mchi/fwts-mchi.o acpi/mpst/fwts-mpst.o acpi/msct/fwts-msct.o acpi/msdm/fwts-msdm.o acpi/method/fwts-method.o acpi/nfit/fwts-nfit.o acpi/osilinux/fwts-osilinux.o acpi/pcc/fwts-pcc.o acpi/pcct/fwts-pcct.o acpi/pdtt/fwts-pdtt.o acpi/powerbutton/fwts-powerbutton.o acpi/plddump/fwts-plddump.o acpi/pmtt/fwts-pmtt.o acpi/pptt/fwts-pptt.o acpi/rasf/fwts-rasf.o acpi/rsdp/fwts-rsdp.o sbbr/rsdp/fwts-rsdp.o acpi/rsdt/fwts-rsdt.o acpi/s3/fwts-s3.o acpi/s3power/fwts-s3power.o acpi/s4/fwts-s4.o acpi/sbst/fwts-sbst.o acpi/sdei/fwts-sdei.o acpi/sdev/fwts-sdev.o acpi/slic/fwts-slic.o acpi/slit/fwts-slit.o acpi/spcr/fwts-spcr.o acpi/spmi/fwts-spmi.o acpi/srat/fwts-srat.o acpi/stao/fwts-stao.o acpi/syntaxcheck/fwts-syntaxcheck.o acpi/tcpa/fwts-tcpa.o acpi/tpm2/fwts-tpm2.o acpi/uefi/fwts-uefi.o acpi/waet/fwts-waet.o acpi/wakealarm/fwts-wakealarm.o acpi/wdat/fwts-wdat.o acpi/wmi/fwts-wmi.o acpi/wpbt/fwts-wpbt.o acpi/wsmt/fwts-wsmt.o acpi/xsdt/fwts-xsdt.o acpi/xenv/fwts-xenv.o apic/apicedge/fwts-apicedge.o bios/bios_info/fwts-bios_info.o bios/bios32/fwts-bios32.o bios/ebda_region/fwts-ebda_region.o bios/ebdadump/fwts-ebdadump.o bios/hdaaudio/fwts-hdaaudio.o bios/memmapdump/fwts-memmapdump.o bios/mtrr/fwts-mtrr.o bios/multiproc/fwts-mpcheck.o bios/multiproc/fwts-mpdump.o bios/pciirq/fwts-pciirq.o bios/pnp/fwts-pnp.o bios/romdump/fwts-romdump.o cmos/cmosdump/fwts-cmosdump.o coreboot/clog/fwts-clog.o cpu/virt/fwts-virt.o cpu/virt/fwts-virt_svm.o cpu/virt/fwts-virt_vmx.o cpu/maxfreq/fwts-maxfreq.o cpu/cpufreq/fwts-cpufreq.o cpu/nx/fwts-nx.o cpu/msr/fwts-msr.o cpu/microcode/fwts-microcode.o dmi/dmicheck/fwts-dmicheck.o hotkey/hotkey/fwts-hotkey.o ipmi/bmc/fwts-bmc_info.o kernel/klog/fwts-klog.o kernel/olog/fwts-olog.o kernel/oops/fwts-oops.o kernel/version/fwts-version.o opal/fwts-mtd_info.o opal/fwts-prd_info.o pci/aspm/fwts-aspm.o pci/crs/fwts-crs.o pci/maxreadreq/fwts-maxreadreq.o uefi/csm/fwts-csm.o uefi/uefidump/fwts-uefidump.o uefi/uefirttime/fwts-uefirttime.o uefi/uefirtvariable/fwts-uefirtvariable.o uefi/uefirtmisc/fwts-uefirtmisc.o uefi/securebootcert/fwts-securebootcert.o uefi/uefivarinfo/fwts-uefivarinfo.o uefi/uefibootpath/fwts-uefibootpath.o uefi/uefirtauthvar/fwts-uefirtauthvar.o uefi/esrtdump/fwts-esrtdump.o uefi/esrt/fwts-esrt.o opal/fwts-pci_info.o opal/fwts-mem_info.o opal/fwts-reserv_mem.o opal/fwts-cpu_info.o opal/fwts-power_mgmt_info.o devicetree/dt_base/fwts-dt_base.o devicetree/dt_sysinfo/fwts-dt_sysinfo.o -L../src/acpica -lfwtsacpica -Llib/src -lfwts -lpci -lfdt -ljson-c 
libtool: link: gcc-9 -g -O2 -o .libs/fwts fwts-main.o acpi/ac_adapter/fwts-ac_adapter.o acpi/acpidump/fwts-acpidump.o acpi/acpiinfo/fwts-acpiinfo.o acpi/acpitables/fwts-acpitables.o sbbr/acpitables/fwts-acpitables.o acpi/apicinstance/fwts-apicinstance.o acpi/asf/fwts-asf.o acpi/aspt/fwts-aspt.o acpi/battery/fwts-battery.o acpi/bert/fwts-bert.o acpi/bgrt/fwts-bgrt.o acpi/boot/fwts-boot.o acpi/brightness/fwts-brightness-helper.o acpi/brightness/fwts-brightness.o acpi/brightness/fwts-autobrightness.o acpi/checksum/fwts-checksum.o acpi/cpep/fwts-cpep.o acpi/crsdump/fwts-crsdump.o acpi/crsdump/fwts-prsdump.o acpi/csrt/fwts-csrt.o acpi/cstates/fwts-cstates.o acpi/dbgp/fwts-dbgp.o acpi/dbg2/fwts-dbg2.o acpi/devices/ac_adapter/fwts-ac.o acpi/devices/battery/fwts-battery.o acpi/devices/battery/fwts-smart_battery.o acpi/devices/ec/fwts-ec.o acpi/devices/buttons/fwts-power_button.o acpi/devices/buttons/fwts-sleep_button.o acpi/devices/lid/fwts-lid.o acpi/devices/sensor/fwts-als.o acpi/devices/time/fwts-time.o acpi/devices/wpc/fwts-wpc.o acpi/dmar/fwts-dmar.o acpi/dppt/fwts-dppt.o acpi/drtm/fwts-drtm.o acpi/dsddump/fwts-dsddump.o acpi/ecdt/fwts-ecdt.o acpi/einj/fwts-einj.o acpi/erst/fwts-erst.o acpi/facs/fwts-facs.o acpi/fadt/fwts-fadt.o sbbr/fadt/fwts-fadt.o acpi/fan/fwts-fan.o acpi/fpdt/fwts-fpdt.o acpi/gpedump/fwts-gpedump.o acpi/gtdt/fwts-gtdt.o acpi/hest/fwts-hest.o acpi/hpet/fwts-hpet.o acpi/hmat/fwts-hmat.o acpi/iort/fwts-iort.o acpi/lid/fwts-lid.o acpi/lpit/fwts-lpit.o acpi/madt/fwts-madt.o acpi/mcfg/fwts-mcfg.o acpi/mchi/fwts-mchi.o acpi/mpst/fwts-mpst.o acpi/msct/fwts-msct.o acpi/msdm/fwts-msdm.o acpi/method/fwts-method.o acpi/nfit/fwts-nfit.o acpi/osilinux/fwts-osilinux.o acpi/pcc/fwts-pcc.o acpi/pcct/fwts-pcct.o acpi/pdtt/fwts-pdtt.o acpi/powerbutton/fwts-powerbutton.o acpi/plddump/fwts-plddump.o acpi/pmtt/fwts-pmtt.o acpi/pptt/fwts-pptt.o acpi/rasf/fwts-rasf.o acpi/rsdp/fwts-rsdp.o sbbr/rsdp/fwts-rsdp.o acpi/rsdt/fwts-rsdt.o acpi/s3/fwts-s3.o acpi/s3power/fwts-s3power.o acpi/s4/fwts-s4.o acpi/sbst/fwts-sbst.o acpi/sdei/fwts-sdei.o acpi/sdev/fwts-sdev.o acpi/slic/fwts-slic.o acpi/slit/fwts-slit.o acpi/spcr/fwts-spcr.o acpi/spmi/fwts-spmi.o acpi/srat/fwts-srat.o acpi/stao/fwts-stao.o acpi/syntaxcheck/fwts-syntaxcheck.o acpi/tcpa/fwts-tcpa.o acpi/tpm2/fwts-tpm2.o acpi/uefi/fwts-uefi.o acpi/waet/fwts-waet.o acpi/wakealarm/fwts-wakealarm.o acpi/wdat/fwts-wdat.o acpi/wmi/fwts-wmi.o acpi/wpbt/fwts-wpbt.o acpi/wsmt/fwts-wsmt.o acpi/xsdt/fwts-xsdt.o acpi/xenv/fwts-xenv.o apic/apicedge/fwts-apicedge.o bios/bios_info/fwts-bios_info.o bios/bios32/fwts-bios32.o bios/ebda_region/fwts-ebda_region.o bios/ebdadump/fwts-ebdadump.o bios/hdaaudio/fwts-hdaaudio.o bios/memmapdump/fwts-memmapdump.o bios/mtrr/fwts-mtrr.o bios/multiproc/fwts-mpcheck.o bios/multiproc/fwts-mpdump.o bios/pciirq/fwts-pciirq.o bios/pnp/fwts-pnp.o bios/romdump/fwts-romdump.o cmos/cmosdump/fwts-cmosdump.o coreboot/clog/fwts-clog.o cpu/virt/fwts-virt.o cpu/virt/fwts-virt_svm.o cpu/virt/fwts-virt_vmx.o cpu/maxfreq/fwts-maxfreq.o cpu/cpufreq/fwts-cpufreq.o cpu/nx/fwts-nx.o cpu/msr/fwts-msr.o cpu/microcode/fwts-microcode.o dmi/dmicheck/fwts-dmicheck.o hotkey/hotkey/fwts-hotkey.o ipmi/bmc/fwts-bmc_info.o kernel/klog/fwts-klog.o kernel/olog/fwts-olog.o kernel/oops/fwts-oops.o kernel/version/fwts-version.o opal/fwts-mtd_info.o opal/fwts-prd_info.o pci/aspm/fwts-aspm.o pci/crs/fwts-crs.o pci/maxreadreq/fwts-maxreadreq.o uefi/csm/fwts-csm.o uefi/uefidump/fwts-uefidump.o uefi/uefirttime/fwts-uefirttime.o uefi/uefirtvariable/fwts-uefirtvariable.o uefi/uefirtmisc/fwts-uefirtmisc.o uefi/securebootcert/fwts-securebootcert.o uefi/uefivarinfo/fwts-uefivarinfo.o uefi/uefibootpath/fwts-uefibootpath.o uefi/uefirtauthvar/fwts-uefirtauthvar.o uefi/esrtdump/fwts-esrtdump.o uefi/esrt/fwts-esrt.o opal/fwts-pci_info.o opal/fwts-mem_info.o opal/fwts-reserv_mem.o opal/fwts-cpu_info.o opal/fwts-power_mgmt_info.o devicetree/dt_base/fwts-dt_base.o devicetree/dt_sysinfo/fwts-dt_sysinfo.o  -lm -lbsd -lgio-2.0 -lgobject-2.0 -lglib-2.0 -L../src/acpica /home/king/repos/fwts/src/acpica/.libs/libfwtsacpica.so -Llib/src /home/king/repos/fwts/src/lib/src/.libs/libfwts.so -lpci -lfdt -ljson-c -Wl,-rpath -Wl,/usr/local/lib/fwts