Don't try to rebuild sxiv during install.

--- sxiv-25/Makefile
+++ sxiv-25/Makefile
@@ -62,7 +62,7 @@
 clean:
 	rm -f *.o sxiv
 
-install: all
+install:
 	@echo "INSTALL bin/sxiv"
 	mkdir -p $(DESTDIR)$(PREFIX)/bin
 	cp sxiv $(DESTDIR)$(PREFIX)/bin/