package/guile: needs libtool

guile build-depends on libtool, but forgot to select it Kconfig.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/guile/Config.in

@@ -8,6 +8,7 @@ config BR2_PACKAGE_GUILE
 	select BR2_PACKAGE_LIBFFI
 	select BR2_PACKAGE_GMP
 	select BR2_PACKAGE_BDWGC
+	select BR2_PACKAGE_LIBTOOL
 	help
 	  Guile is an interpreter and compiler for the Scheme
 	  programming language, a clean and elegant dialect of Lisp.