gettext-tools: add missing dependency in libiconv for Windows

recipes/build-tools/gettext-tools.recipe

@@ -9,7 +9,9 @@ class Recipe(recipe.Recipe):
     stype = SourceType.TARBALL
     tarball_dirname = 'gettext-%(version)s'
     url = 'http://ftp.gnu.org/pub/gnu/gettext/gettext-0.18.2.tar.gz'
-    platform_deps = {Platform.DARWIN:  ['libiconv', 'sed']}
+    platform_deps = {
+            Platform.DARWIN:  ['libiconv', 'sed'],
+            Platform.WINDOWS: ['libiconv'],}
     configure_options = ' --disable-java --disable-csharp --disable-native-java --without-csv'
 
     def prepare(self):