It will be required by ICU 61 anyway, see
https://ssl.icu-project.org/repos/icu/trunk/icu4c/readme.html#RecBuild

Change-Id: If7f1330550981fd28eb7eea6329f21e116291cca
Reviewed-on: https://gerrit.libreoffice.org/46740Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>
Reviewed-on: https://gerrit.libreoffice.org/56779
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
(cherry picked from commit 3aabc93b)