build: added DragonFly BSD

Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>
diff --git a/Makefile b/Makefile
index 6670a4d..3737e69 100644
--- a/Makefile
+++ b/Makefile
@@ -42,6 +42,9 @@
 ifeq ($(UNAME_S), FreeBSD)
 LIBDATADIR = $(DESTDIR)$(PREFIX)/libdata
 endif
+ifeq ($(UNAME_S), DragonFly)
+LIBDATADIR = $(DESTDIR)$(PREFIX)/libdata
+endif
 
 INSTALL_BIN ?= install
 INSTALL_DATA ?= $(INSTALL_BIN) -m0644