dumpbin doesn't exist in mingw

configure.ac

@@ -645,7 +645,13 @@ case "${host}" in
 	  DSO_LDFLAGS="-shared"
 	  link_whole_archive="1"
 	fi
+	case "${host}" in
+	  *-*-cygwin*)
 	    DUMP_SYMS="dumpbin /SYMBOLS"
+	    ;;
+	  *)
+	    ;;
+	esac
 	a="lib"
 	libprefix=""
 	SOREV="${so}"