eolian: add API to get full file path of a unit

This is necessary for easy dependency generation, as it is needed
to retrieve a full list of paths that each generated file depends
on.

src/lib/eolian/Eolian.h

@@ -909,10 +909,26 @@ EAPI Eina_Iterator *eolian_unit_children_get(const Eolian_Unit *unit);
  *
  * @param[in] unit The unit.
  *
+ * @see eolian_unit_file_path_get
+ *
  * @ingroup Eolian
  */
 EAPI const char *eolian_unit_file_get(const Eolian_Unit *unit);
 
+/*
+ * @brief Get the full file path a unit is associated with.
+ *
+ * This will be `NULL` if not associated with a file (like the master unit
+ * within `Eolian_State`).
+ *
+ * @param[in] unit The unit.
+ *
+ * @see eolian_unit_file_get
+ *
+ * @ingroup Eolian
+ */
+EAPI const char *eolian_unit_file_path_get(const Eolian_Unit *unit);
+
 /*
  * @brief Get an object in a unit by name.
  *

src/lib/eolian/eolian_database.c

@@ -1226,6 +1226,16 @@ eolian_unit_file_get(const Eolian_Unit *unit)
    return unit->file;
 }
 
+EAPI const char *
+eolian_unit_file_path_get(const Eolian_Unit *unit)
+{
+   if (!unit || !unit->file) return NULL;
+   Eina_Bool is_eo = eina_str_has_suffix(unit->file, EO_SUFFIX);
+   return eina_hash_find(is_eo
+     ? unit->state->filenames_eo
+     : unit->state->filenames_eot, unit->file);
+}
+
 EAPI const Eolian_Object *
 eolian_unit_object_by_name_get(const Eolian_Unit *unit, const char *name)
 {