socket: Set SOCK_CLOEXEC if available
socket: Set SOCK_CLOEXEC if available

Reported by Марк Коренберг <socketpair@gmail.com>

cyclops8456/libnl3,congwang/libnl,cfriedt/libnl,karlhiramoto/libnl,vyos/libnl3,HolyShitMan/libnl-1,UnicronNL/libnl3,teto/libnl_old,HolyShitMan/libnl-1,chitranshi/libnl,baloo/libnl,teto/libnl_old,cfriedt/libnl,cfriedt/libnl,claudelee/libnl,chitranshi/libnl,baloo/libnl,tgraf/libnl,mshirley/libnl,karlhiramoto/libnl,baloo/libnl,Distrotech/libnl,teto/libnl_old,vyos/libnl3,mshirley/libnl,Distrotech/libnl,thom311/libnl,kolyshkin/libnl,teto/libnl_old,claudelee/libnl,greearb/libnl-ct,greearb/libnl-ct,tgraf/libnl,kolyshkin/libnl,houstar/libnl,socketpair/libnl,Distrotech/libnl,UnicronNL/libnl3,honsys/libnl,cyclops8456/libnl3,congwang/libnl,baloo/libnl,houstar/libnl,chitranshi/libnl,dsahern/libnl,mshirley/libnl,cfriedt/libnl,claudelee/libnl,chitranshi/libnl,tgraf/libnl,tklauser/libnl,claudelee/libnl,dsahern/libnl,honsys/libnl,tklauser/libnl,tklauser/libnl,socketpair/libnl,kolyshkin/libnl,cyclops8456/libnl3,vyos/libnl3,congwang/libnl,honsys/libnl,mshirley/libnl,tgraf/libnl,honsys/libnl,socketpair/libnl,tklauser/libnl,gxk/libnl,Distrotech/libnl,HolyShitMan/libnl-1,UnicronNL/libnl3,congwang/libnl,dsahern/libnl,karlhiramoto/libnl,thom311/libnl,vyos/libnl3,gxk/libnl,HolyShitMan/libnl-1,houstar/libnl,greearb/libnl-ct,houstar/libnl,kolyshkin/libnl,cyclops8456/libnl3,karlhiramoto/libnl,gxk/libnl,UnicronNL/libnl3,thom311/libnl,dsahern/libnl