build: Port meson-make-symlink script to Python

Instead of using non-portable features of GNU ln command, such as -T
and --relative, use Python os.path.relpath function to handle it. This
fixes installation failure on FreeBSD.

meson.build

@@ -13,7 +13,7 @@ gnome = import('gnome')
 i18n = import('i18n')
 pkgconfig = import('pkgconfig')
 
-meson_make_symlink = join_paths(meson.source_root(), 'tools', 'meson-make-symlink.sh')
+meson_make_symlink = join_paths(meson.source_root(), 'tools', 'meson-make-symlink.py')
 po_dir = join_paths(meson.source_root(), 'po')
 
 prefix = get_option('prefix')

tools/meson-make-symlink.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+
+destdir = os.environ.get('DESTDIR')
+source = sys.argv[1]
+target = sys.argv[2]
+
+def prepend_destdir(path):
+    if destdir is not None:
+        if os.path.isabs(path):
+            return os.path.join(destdir, path[1:])
+        else:
+            return os.path.join(destdir, path)
+    else:
+        return path
+
+def call_symlink(src, dst):
+    try:
+        os.remove(dst)
+    except:
+        pass
+    os.symlink(src, dst)
+
+os.makedirs(os.path.dirname(prepend_destdir(target)), exist_ok=True)
+if os.path.dirname(source) == '.':
+    destdir_target = prepend_destdir(target)
+    call_symlink(source, destdir_target)
+else:
+    destdir_source = prepend_destdir(source)
+    destdir_target = prepend_destdir(target)
+    destdir_target_dir = os.path.dirname(destdir_target)
+    relative_source = os.path.relpath(destdir_source, destdir_target_dir)
+    call_symlink(relative_source, destdir_target)

tools/meson-make-symlink.sh

@@ -1,12 +0,0 @@
-#!/bin/sh
-set -eu
-
-# this is needed mostly because $DESTDIR is provided as a variable,
-# and we need to create the target directory...
-
-mkdir -vp "$(dirname "${DESTDIR:-}$2")"
-if [ "$(dirname $1)" = . ]; then
-        ln -vfs -T "$1" "${DESTDIR:-}$2"
-else
-        ln -vfs -T --relative "${DESTDIR:-}$1" "${DESTDIR:-}$2"
-fi