glib-mkenums: fix @filename@ in file-head/-tail

If @filename@ or @basename@ are used in the head and tail of the
template, the path/basename of the first and last file to be processed
are substituted.

9023fa350d6271811e75d06848a3772fff8588b1 sorts the list of files being
processed, in the name of producing reproducible output regardless of
command-line ordering. But this was done only when iterating the files,
not when generating the head and tail. For consistency, sort sooner.

gobject/glib-mkenums.in

@@ -415,6 +415,8 @@ def replace_specials(prod):
     prod = prod.rstrip()
     return prod
 
+options.args.sort()
+
 if len(fhead) > 0:
     prod = fhead
     base = os.path.basename(options.args[0])
@@ -707,7 +709,7 @@ def process_file(curfilename):
                 prod = replace_specials(prod)
                 write_output(prod)
 
-for fname in sorted(options.args):
+for fname in options.args:
     process_file(fname)
 
 if len(ftail) > 0: