Build dynamically linked executables by default

This patch is related to the following issue:

https://github.com/genodelabs/genode/issues/2184

run/remote_rom_backend_nic_ip_server.run

@@ -77,7 +77,7 @@ install_config {
 # Boot image
 #
 
-build_boot_image { core init timer
+build_boot_image { core ld.lib.so init timer
 	remote_rom_server
 	dynamic_rom
 	nic_drv