Makefile: Fix `make install` into empty DESTDIR
My `makesudoinstall` script:
broke due to the previous change to move the binary into the srcdir.
@@ -14,6 +14,7 @@ mantle:
install:
install -d $(DESTDIR)$(PREFIX)/lib/coreos-assembler
install -D -t $(DESTDIR)$(PREFIX)/lib/coreos-assembler $$(find src/ -maxdepth 1 -type f)
+ install -d $(DESTDIR)$(PREFIX)/bin
ln -sf ../lib/coreos-assembler/coreos-assembler $(DESTDIR)$(PREFIX)/bin/
install -D -t $(DESTDIR)$(PREFIX)/bin mantle/bin/{ore,kola}
install -d $(DESTDIR)$(PREFIX)/lib/kola/amd64
