Merge topic 'lang-platform-flags'

0b24c94676 Modules: Fix per-language fallback to platform-specific shared module C flags
ae1d5ef47f Modules: Initialize per-language platform-specific flag variables consistently

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !9526