elf2flt: needs to link with zlib

Got dropped by the move to packages/.

Fixes http://autobuild.buildroot.net/results/bb7/bb7b2c0bb23e0ab6e148a1e690b2c0827135ff55/

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/elf2flt/elf2flt.mk

@@ -21,6 +21,8 @@ HOST_ELF2FLT_CONF_OPT = \
 	--with-libiberty=$(HOST_BINUTILS_DIR)/libiberty/libiberty.a \
 	--target=$(GNU_TARGET_NAME)
 
+HOST_ELF2FLT_CONF_ENV = LIBS=-lz
+
 define HOST_ELF2FLT_EXTRACT_CMDS
 	cp -r package/elf2flt/src/* $(@D)
 endef