meta-phosphor: phosphor-dbus-interfaces: add explicit task-dep on unpack

The recipe has an extension to the `do_write_config` task that
forces all of the YAML subdirectory options to `false` using the list
in the `meson_options.txt`.  Since we are parsing the
`meson_options.txt`, we need it to be present, so we need to explicitly
rely on the `do_unpack` task.

Tested:

The `log.task_order` has the correct order.
```
$ cat log.task_order
20230113-151838.797418 do_fetch (3200585): log.do_fetch.3200585
20230113-151840.771096 do_unpack (3201820): log.do_unpack.3201820
20230113-151842.762491 do_write_config (3202881): log.do_write_config.3202881
```
Ran `bitbake phosphor-dbus-interfaces -ne` and examined the `taskdeps`
structure to confirm the dependency is added.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I0d81d127fd1bda39eeb38e6ce89614e1f4ddfa30
diff --git a/meta-phosphor/recipes-phosphor/dbus/phosphor-dbus-interfaces_git.bb b/meta-phosphor/recipes-phosphor/dbus/phosphor-dbus-interfaces_git.bb
index 6962469..4dbc470 100644
--- a/meta-phosphor/recipes-phosphor/dbus/phosphor-dbus-interfaces_git.bb
+++ b/meta-phosphor/recipes-phosphor/dbus/phosphor-dbus-interfaces_git.bb
@@ -39,3 +39,4 @@
         sed -i "/^\[built-in options\]\$/a$intf = false" ${WORKDIR}/meson.cross
     done
 }
+do_write_config[deptask] += "do_unpack"