packaging/generic-unix: Fix the way we path files list to tar(1)

If we use xargs(1) to call tar(1), we are limited by the number of
arguments we can put on the command line. Since we switch to use
directories to "package" plugins instead of .ez archives, the number of
files exploded. This led to incomplete generic-unix archives (i.e. some
plugins and CLI scripts were missing for instance).

Now, the list of files is written to a manifest, exactly like we do it
to create the source archive.

packaging/generic-unix/Makefile

@@ -66,8 +66,8 @@ dist:
 
 	mkdir -p $(TARGET_DIR)/etc/rabbitmq
 
-	find $(TARGET_DIR) -print0 | LC_COLLATE=C sort -z | \
-	xargs -0 tar --no-recursion -cf - | \
+	find $(TARGET_DIR) | LC_COLLATE=C sort > $(TARGET_TARBALL).manifest
+	tar --no-recursion -T $(TARGET_TARBALL).manifest -cf - | \
 	xz > $(CURDIR)/$(TARGET_TARBALL).tar.xz
 
 	if test "$(PACKAGES_DIR)"; then \