meson: add depend_files for gl_enums.py

gl_enums.py depends on (at least):
- license.py
- gl_XML.py
- some XML files

Adding glapi_xml_py_deps to make sure that ninja-to-soong can produce
valid blueprint for Android

Ref #14072

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37865>

src/mesa/glapi/glapi/gen/meson.build

@@ -24,6 +24,7 @@ main_enums_c = custom_target(
   input : ['gl_enums.py', files('../registry/gl.xml')],
   output : 'enums.c',
   command : [prog_python, '@INPUT0@', '-f', '@INPUT1@'],
+  depend_files : glapi_xml_py_deps,
   capture : true,
 )