[meld] build_helpers: Fix build for fake makefile addition

[Kai Willadsen <kaiw src gnome org>]

commit 176e7c83dcc65ee39010fbd1a546ffbaac597062
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Tue Nov 21 05:56:40 2017 +1000

    build_helpers: Fix build for fake makefile addition

 meld/build_helpers.py |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/meld/build_helpers.py b/meld/build_helpers.py
index c8bdac9..caa0b98 100644
--- a/meld/build_helpers.py
+++ b/meld/build_helpers.py
@@ -113,7 +113,9 @@ class build_help(distutils.cmd.Command):
         if "LINGUAS" in os.environ:
             self.selected_languages = os.environ["LINGUAS"].split()
         else:
-            self.selected_languages = os.listdir(self.help_dir)
+            self.selected_languages = [
+                d for d in os.listdir(self.help_dir) if os.path.isdir(d)
+            ]
 
         if 'C' not in self.selected_languages:
             self.selected_languages.append('C')