Remove unnecessary volume mount argument.

Reviewed at https://reviews.apache.org/r/40666/
diff --git a/build-artifact.sh b/build-artifact.sh
index 0bb7ea6..333c7a4 100755
--- a/build-artifact.sh
+++ b/build-artifact.sh
@@ -36,7 +36,6 @@
     -e AURORA_VERSION=$AURORA_VERSION \
     -v "$(pwd)/specs:/specs:ro" \
     -v "$(realpath $RELEASE_TAR):/src.tar.gz:ro" \
-    -v "$ARTIFACT_DIR:/dist" \
     -t "$IMAGE_NAME" /build.sh
   container=$(docker ps -l -q)
   artifact_dir="artifacts/$IMAGE_NAME"