[gcab] folder: simplify _sort_cfiles()

[Marc-André Lureau <malureau src gnome org>]

commit 76bc71a4b385909c472a481a39c7a5b9c6ac5164
Author: Marc-André Lureau <marcandre lureau redhat com>
Date:   Tue Jan 23 18:30:57 2018 +0100

    folder: simplify _sort_cfiles()
    
    Get rid of warnings such as:
    libgcab/gcab-folder.c: In function ‘_sort_cfiles’:
    libgcab/gcab-folder.c:215:43: warning: passing argument 1 of ‘gcab_file_get_name’ discards ‘const’ 
qualifier from pointer target type [-Wdiscarded-qualifiers]
         return g_strcmp0 (gcab_file_get_name (file_a), gcab_file_get_name (file_b));
                                               ^~~~~~
    by casting the compare function.
    
    Signed-off-by: Marc-André Lureau <marcandre lureau redhat com>

 libgcab/gcab-folder.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)
---
diff --git a/libgcab/gcab-folder.c b/libgcab/gcab-folder.c
index be3459d..1b09fa3 100644
--- a/libgcab/gcab-folder.c
+++ b/libgcab/gcab-folder.c
@@ -208,10 +208,8 @@ add_file (GCabFolder *self, GCabFile *file, GError **error)
 #define FILE_ATTRS "standard::*,time::modified"
 
 static gint
-_sort_cfiles (gconstpointer a, gconstpointer b)
+_sort_cfiles (GCabFile *file_a, GCabFile *file_b)
 {
-    GCabFile *file_a = GCAB_FILE (a);
-    GCabFile *file_b = GCAB_FILE (b);
     return g_strcmp0 (gcab_file_get_name (file_a), gcab_file_get_name (file_b));
 }
 
@@ -242,7 +240,7 @@ add_file_info (GCabFolder *self, GCabFile *file, GFileInfo *info,
             }
 
             /* sort the files to avoid depending on filesystem order */
-            self->files = g_slist_sort (self->files, _sort_cfiles);
+            self->files = g_slist_sort (self->files, (GCompareFunc)_sort_cfiles);
 
             g_object_unref (info);
         }