These arrays should have been declared extern in the first place.
Newer versions of gcc now complain about this:
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: client/dbus-proxy.o:(.bss+0x0): multiple definition of `properties_yes_no_opts'; client/adapter.o:(.bss+0x0): first defined here
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: client/dbus-proxy.o:(.bss+0x20): multiple definition of `properties_on_off_opts'; client/adapter.o:(.bss+0x20): first defined here
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: client/device.o:(.bss+0x20): multiple definition of `properties_on_off_opts'; client/adapter.o:(.bss+0x20): first defined here
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: client/device.o:(.bss+0x0): multiple definition of `properties_yes_no_opts'; client/adapter.o:(.bss+0x0): first defined here
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: client/known-networks.o:(.bss+0x0): multiple definition of `properties_yes_no_opts'; client/adapter.o:(.bss+0x0): first defined here
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: client/known-networks.o:(.bss+0x20): multiple definition of `properties_on_off_opts'; client/adapter.o:(.bss+0x20): first defined here
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: client/properties.o:(.data.rel.local+0x0): multiple definition of `properties_yes_no_opts'; client/adapter.o:(.bss+0x0): first defined here
/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/../../../../x86_64-pc-linux-gnu/bin/ld: client/properties.o:(.data.rel.local+0x20): multiple definition of `properties_on_off_opts'; client/adapter.o:
