Bump mingw-check CI image from Ubuntu 16.04 to 18.04.

diff --git a/src/ci/docker/mingw-check/Dockerfile b/src/ci/docker/mingw-check/Dockerfile
index 97e4d3fd7499e92ad4fbbc63a0f8efc52756c4f5..21ec8bbe4b1ec7e406d5b642c90ec6d6d8ab2885 100644 (file)
--- a/src/ci/docker/mingw-check/Dockerfile
+++ b/src/ci/docker/mingw-check/Dockerfile
@@ -1,4 +1,4 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
   g++ \