lib.interlink: take advantage of non-excl shm.create semantics
lib.interlink: take advantage of non-excl shm.create semantics

shm.create does not ask for O_EXCL to open(2), so we don’t actually need to do
the pcall dance in attach. Part of me thinks maybe we should ask for O_EXCL in
shm.create, but OTOH this way the code is simpler…

eugeneia/snabb,Igalia/snabb,Igalia/snabbswitch,alexandergall/snabbswitch,eugeneia/snabb,eugeneia/snabb,dpino/snabbswitch,eugeneia/snabbswitch,Igalia/snabbswitch,Igalia/snabb,Igalia/snabbswitch,dpino/snabb,alexandergall/snabbswitch,alexandergall/snabbswitch,snabbco/snabb,alexandergall/snabbswitch,Igalia/snabbswitch,dpino/snabb,SnabbCo/snabbswitch,snabbco/snabb,Igalia/snabb,eugeneia/snabbswitch,Igalia/snabb,SnabbCo/snabbswitch,Igalia/snabb,dpino/snabb,alexandergall/snabbswitch,alexandergall/snabbswitch,snabbco/snabb,Igalia/snabb,snabbco/snabb,snabbco/snabb,dpino/snabbswitch,eugeneia/snabb,eugeneia/snabbswitch,dpino/snabb,eugeneia/snabb,Igalia/snabbswitch,dpino/snabb,dpino/snabb,Igalia/snabb,eugeneia/snabb,snabbco/snabb,alexandergall/snabbswitch,snabbco/snabb,eugeneia/snabbswitch,eugeneia/snabb,SnabbCo/snabbswitch,alexandergall/snabbswitch,dpino/snabbswitch,dpino/snabb,eugeneia/snabb,Igalia/snabb,snabbco/snabb,dpino/snabbswitch,SnabbCo/snabbswitch