blktap2/vhd: add -liconv when linking if using libiconv

If libiconv is detected on the system add -liconv when linking the
libvhd library.

If -liconv is not added when compiling libvhd with libiconv the
following error occours when linking vhd-util and vhd-update:

gcc     -o vhd-util vhd-util.o -Llib -lvhd
lib/libvhd.so: undefined reference to `libiconv_open'
lib/libvhd.so: undefined reference to `libiconv_close'
lib/libvhd.so: undefined reference to `libiconv'

Signed-off-by: Roger Pau Monne <roger.pau@entel.upc.edu>
Committed-by: Ian Jackson <ian.jackson.citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/blktap2/vhd/lib/Makefile

@@ -23,6 +23,10 @@ ifeq ($(CONFIG_Linux),y)
 LIBS            := -luuid
 endif
 
+ifeq ($(CONFIG_LIBICONV),y)
+LIBS            += -liconv
+endif
+
 LIB-SRCS        := libvhd.c
 LIB-SRCS        += libvhd-journal.c
 LIB-SRCS        += vhd-util-coalesce.c