util/gen_xmlpool: Don't write via shell redirection

Using shell redirection to write to a file is more complicated than
necessary, and has the potential to run into unicode encoding problems.
It's also less code.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108530

v2: - update commit message to say less about LANG=C
    - use flags instead of positional arguments for the script (Emil)

Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/util/xmlpool/SConscript

@@ -8,7 +8,7 @@ xmlpool_options, = env.CodeGenerate(
     target = 'options.h',
     script = 'gen_xmlpool.py',
     source = ['t_options.h'],
-    command = python_cmd + ' $SCRIPT $SOURCE ' + LOCALEDIR + ' > $TARGET'
+    command = python_cmd + ' $SCRIPT --template $SOURCE --output $TARGET --localedir ' + LOCALEDIR
 )
 
 Export('xmlpool_options')