libcgroup: also needs host-flex

Fixes:
http://autobuild.buildroot.net/results/b43/b43ef442facd5aa136a77db99e57e02cc7e39a94/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libcgroup/libcgroup.mk

@@ -9,7 +9,7 @@ LIBCGROUP_SOURCE = libcgroup-$(LIBCGROUP_VERSION).tar.bz2
 LIBCGROUP_SITE = http://downloads.sourceforge.net/project/libcg/libcgroup/v.038
 LIBCGROUP_LICENSE = LGPLv2.1
 LIBCGROUP_LICENSE_FILES = COPYING
-LIBCGROUP_DEPENDENCIES = host-bison
+LIBCGROUP_DEPENDENCIES = host-bison host-flex
 LIBCGROUP_INSTALL_STAGING = YES
 
 # Undefining _FILE_OFFSET_BITS here because of a "bug" with glibc fts.h