Bug 1462859 - Add --disable-layoutex when running ICU configure. r=froydnj

In some recent ICU update, --enable-layoutex changed from defaulting to
the "same-as-layout" to "yes", so --disable-layout doesn't imply
--disable-layoutex anymore, but we removed the layoutex files.

--HG--
extra : rebase_source : 4343c37d840aec94adcb8ccb7571969d6c0979e0

intl/icu_sources_data.py

@@ -123,6 +123,7 @@ def update_data_file(topsrcdir):
              '--disable-extras',
              '--disable-icuio',
              '--disable-layout',
+             '--disable-layoutex',
              '--disable-tests',
              '--disable-samples',
              '--disable-strict'],