Configure network interfaces by default

For an optimal out-of-the-box experience, we need to automatically
configure any wired network interfaces with DHCP.  `systemd-networkd`
does not do this by default.

package/aimee-os-utils/90-default.network

@@ -0,0 +1,10 @@
+[Match]
+Type=ether
+Name=en* eth*
+
+[Network]
+DHCP=true
+
+[DHCPv4]
+ClientIdentifier=mac
+UseDomain=true

package/aimee-os-utils/aimee-os-utils.mk

@@ -23,6 +23,9 @@ define AIMEE_OS_UTILS_INSTALL_INIT_SYSTEMD
 	$(INSTALL) -D -m u=rw,go=r \
 		$(AIMEE_OS_UTILS_PKGDIR)/var.mount \
 		$(TARGET_DIR)/usr/lib/systemd/system/var.mount
+	$(INSTALL) -D -m u=rw,go=r \
+		$(AIMEE_OS_UTILS_PKGDIR)/90-default.network \
+		$(TARGET_DIR)/usr/lib/systemd/network/90-default.network
 endef
 
 $(eval $(generic-package))