Isolate building packages some more

Don't load the user init file while building my Emacs packages, make sure to use
a different ‘package-user-dir’ so that bad packages don't interfere and it
doesn't accidentally work because of existing packages. Specify the
‘package-archive-upload-base’ in the Makefile so that there is only one place to
look and modify if this needs to move. Ensure that the
‘package-archive-upload-base’ exists before uploading to it.

GNUmakefile

@@ -3,10 +3,13 @@ FILES := $(wildcard oni-*.el)
 PACKAGE_TARGETS := $(addprefix package-,$(FILES))
 
 define upload =
-	emacs --batch \
+	emacs --quick --batch \
+	    --eval "(setq package-user-dir \"local-elpa/\")" \
 	    --load oni-package.el \
 	    --funcall package-initialize \
-	    --eval "(package-upload-file $1)"
+	    --eval "(let ((package-archive-upload-base \"bin/\")) \
+                  (mkdir package-archive-upload-base t) \
+                  (package-upload-file $1))"
 endef
 
 define upload-multi-file =