Set --with-online-update-mar-channel for distro-configs/LibreOfficeWin64.conf

(Somewhat randomly setting it to the same name that is used, via
-DMAR_CHANNEL_ID=\"LOOnlineUpdater\" in external/onlineupdate/Executable_mar.mk,
as the default channel name in the mar executable tool that we build.)

Change-Id: Ia77e3e841139947dad894efa81f011cafd6c7539
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/161049
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>
(cherry picked from commit 535a03cb946d48c91863943665b01123ac23ba0a)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/161019
diff --git a/distro-configs/LibreOfficeWin64.conf b/distro-configs/LibreOfficeWin64.conf
index 8ace248..a8efd04 100644
--- a/distro-configs/LibreOfficeWin64.conf
+++ b/distro-configs/LibreOfficeWin64.conf
@@ -8,6 +8,7 @@
--enable-ext-nlpsolver
--enable-online-update
--enable-online-update-mar
--with-online-update-mar-channel=LOOnlineUpdater
--enable-breakpad
--with-help=html
--with-myspell-dicts