Bug 1439726 Add patch to the MinGW Dockerfile r=glandium

MozReview-Commit-ID: DIzDSnNHzfM

--HG--
extra : rebase_source : c4de09802785e1802e76898d820d0d9cf87896ed

taskcluster/docker/mingw32-build/Dockerfile

@@ -25,6 +25,7 @@ RUN apt-get update && \
       g++-multilib \
       gnupg \
       libucl-dev \
+      patch \
       p7zip-full \
       scons \
       tar \