build: fix libftd2xx regression

Fix build when targeting closed src ftd2xx drivers.
configure is unable to find the dynamic linking loader lib (dl) as it
is included before ftd2xx library.

Change-Id: Ibe7308b66ed846288a31f7a27ff549b6f39baeec
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/1355
Tested-by: jenkins
Reviewed-by: Luca Bruno <lucab@debian.org>
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

configure.ac

@@ -961,7 +961,7 @@ if test $build_ft2232_ftd2xx = yes -o $build_presto_ftd2xx = yes -o $build_usb_b
       fi
     fi
     LDFLAGS="${LDFLAGS} ${FTD2XX_LDFLAGS}"
-    LIBS="${LIBS} ${FTD2XX_LIB}"
+    LIBS="${FTD2XX_LIB} ${LIBS}"
     AC_MSG_RESULT([${FTD2XX_LDFLAGS} ${FTD2XX_LIB}])
   else
     AC_CHECK_HEADER([ftd2xx.h],[],[