scripts: Add script to generate OSv VMware configuration

./scripts/gen-vmx.sh will create build/release/osv.vmx
You can run this VM image on VMware by executing following command:
vmware build/release/osv.vmx

Signed-off-by: Takuya ASADA <syuu@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>