net/mediatomb: Unbreak build with GCC 10 (-fno-common default)

/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-gena_device.o):(.bss+0x20): multiple definition of `gUserHTTPHeaders'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xc80): first defined here
/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-gena_device.o):(.bss+0x0): multiple definition of `gMaxHTTPTimeoutRetries'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xc70): first defined here
/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-gena_device.o):(.bss+0x4): multiple definition of `gUpnpSdkShutdown'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xc74): first defined here
/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-gena_device.o):(.bss+0x40): multiple definition of `pUserHTTPHeaderList'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xca0): first defined here
/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-gena_device.o):(.bss+0x48): multiple definition of `pVirtualDirList'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xca8): first defined here
/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-miniserver.o):(.bss+0x4): multiple definition of `gMaxHTTPTimeoutRetries'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xc70): first defined here
/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-miniserver.o):(.bss+0x8): multiple definition of `gUpnpSdkShutdown'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xc74): first defined here
/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-miniserver.o):(.bss+0x20): multiple definition of `gUserHTTPHeaders'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xc80): first defined here
/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-miniserver.o):(.bss+0x40): multiple definition of `pUserHTTPHeaderList'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xca0): first defined here
/usr/local/bin/ld: ../tombupnp/build/libtombupnp.a(libtombupnp_a-miniserver.o):(.bss+0x48): multiple definition of `pVirtualDirList'; ../tombupnp/build/libtombupnp.a(libtombupnp_a-upnpapi.o):(.bss+0xca8): first defined here

http://package22.nyi.freebsd.org/data/113amd64-default-PR244008/2020-06-10_18h05m01s/logs/errors/mediatomb-0.12.1_26.log

PR: 246700