I need this bit too

target/device/Soekris/Config.in

@@ -2,6 +2,14 @@ config BR2_TARGET_SOEKRIS_NET4521
 	bool "Soekris net4521"
 	depends BR2_i386
 	default n
+	select BR2_PACKAGE_LINUX
 	help
 	  The Soekris net4521
 
+config BR2_PACKAGE_LINUX
+	bool "linux"
+	default n
+	help
+	    The Linux kernel.
+
+	    http://www.kernel.org/