build: link with libkvm on openbsd
build: link with libkvm on openbsd

The Makefile already did and now the gyp build does too. Fixes the
OpenBSD build of node.js.

Fixes joyent/node#5363.

urbit/archaeology2,unknownbrackets/maxcso,urbit/archaeology2,unknownbrackets/maxcso,unknownbrackets/maxcso,urbit/archaeology2,urbit/archaeology2,urbit/archaeology2,urbit/archaeology2,unknownbrackets/maxcso,urbit/archaeology2,urbit/archaeology2,unknownbrackets/maxcso,urbit/archaeology2,unknownbrackets/maxcso,unknownbrackets/maxcso