bc: needs host-flex

Fixes:
http://autobuild.buildroot.net/results/49d/49d78f0528c6ecc2adfcfa17f4b09ec225c594be/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/bc/bc.mk

@@ -6,6 +6,7 @@
 
 BC_VERSION = 1.06
 BC_SITE = $(BR2_GNU_MIRROR)/bc/
+BC_DEPENDENCIES = host-flex
 BC_LICENSE = GPLv2+ LGPLv2.1+
 BC_LICENSE_FILES = COPYING COPYING.LIB