ci(github): use grouping also in the `win-build` job

We already do the same when building Git in all the other jobs.

This will allow us to piggy-back on top of grouping to mark up compiler
errors in the next commit.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ci/make-test-artifacts.sh

@@ -7,6 +7,6 @@ mkdir -p "$1" # in case ci/lib.sh decides to quit early
 
 . ${0%/*}/lib.sh
 
-make artifacts-tar ARTIFACTS_DIRECTORY="$1"
+group Build make artifacts-tar ARTIFACTS_DIRECTORY="$1"
 
 check_unignored_build_artifacts