meson: Use Python port of glib-mkenums

This reduces the build-time dependencies of glib to only Python 3,
Meson, and git. Git is also optional if you provide a tarball in
which the subproject directories already exist.

The Python port was done by Jussi Pakkanen on bugzilla:
https://bugzilla.gnome.org/show_bug.cgi?id=779332

This version contains some fixes from that and also changes all
instances of `@` to `\u0040` because Meson does not yet provide a
configure_file() mode that ignores unknown @MACRO@ values.

gio/build_mkenum.py

@@ -7,7 +7,7 @@
 
 import sys, os, shutil, subprocess
 
-perl = sys.argv[1]
+python = sys.argv[1]
 glib_mkenums = sys.argv[2]
 ofilename = sys.argv[3]
 ofile_rel = os.path.basename(ofilename)
@@ -17,7 +17,7 @@ headers = sys.argv[5:]
 
 arg_array = ['--template', template_file_path]
 
-cmd = [perl, glib_mkenums]
+cmd = [python, glib_mkenums]
 pc = subprocess.Popen(cmd + arg_array + headers, stdout=subprocess.PIPE)
 (stdo, _) = pc.communicate()
 if pc.returncode != 0:

gio/meson.build

@@ -640,7 +640,7 @@ gioenumtypes_h = custom_target('gioenumtypes_h',
   input : gio_headers,
   install : true,
   install_dir : join_paths(get_option('includedir'), 'glib-2.0/gio'),
-  command : [gio_build_mkenum, perl, glib_mkenums,
+  command : [gio_build_mkenum, python, glib_mkenums,
              '@OUTPUT@', meson.current_source_dir(),
              '@INPUT@', gnetworking_h])
 
@@ -648,7 +648,7 @@ gioenumtypes_c = custom_target('gioenumtypes_c',
   output : 'gioenumtypes.c',
   input : gio_headers,
   depends : [gioenumtypes_h],
-  command : [gio_build_mkenum, perl, glib_mkenums,
+  command : [gio_build_mkenum, python, glib_mkenums,
              '@OUTPUT@', meson.current_source_dir(),
              '@INPUT@', gnetworking_h])
 

gobject/meson.build

@@ -68,7 +68,6 @@ libgobject_dep = declare_dependency(link_with : libgobject,
 
 glib_mkenums_conf = configuration_data()
 glib_mkenums_conf.set('GLIB_VERSION', glib_version)
-glib_mkenums_conf.set('PERL_PATH', perl.path())
 
 # FIXME: Set permissions
 glib_mkenums = configure_file(input : 'glib-mkenums.in',

meson.build

@@ -1304,9 +1304,6 @@ if host_system == 'windows'
   winsock2 = cc.find_library('ws2_32')
 endif
 
-# Needed for glib-mkenums
-perl = find_program('perl')
-
 python = import('python3').find_python()
 
 # FIXME: defines in config.h that are not actually used anywhere