wine build: use docker to (try to) have reproducible builds

contrib/build-wine/docker/README.md

@@ -0,0 +1,42 @@
+Deterministic Windows binaries with Docker
+==========================================
+
+This assumes an Ubuntu host, but it should not be too hard to adopt to another
+similar system.
+
+1. Install Docker
+
+    ```
+    $ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
+    $ sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
+    $ sudo apt-get update
+    $ sudo apt-get install -y docker-ce
+    ```
+
+2. Build image
+
+    ```
+    $ cd contrib/build-wine/docker
+    $ PROJECT_ROOT=$(pwd)/../../../
+    $ sudo docker build --no-cache -t electrum-wine-builder-img .
+    ```
+
+    Note: see [this](https://stackoverflow.com/a/40516974/7499128) if having dns problems
+
+3. Build Windows binaries
+
+    ```
+    $ TARGET=master
+    $ sudo docker run \
+        --name electrum-wine-builder-cont \
+        -v ${PROJECT_ROOT}:/opt/electrum \
+        --rm \
+        --workdir /opt/electrum/contrib/build-wine \
+        electrum-wine-builder-img \
+        ./build.sh $TARGET
+    ```
+4. The generated binaries are in `$PROJECT_ROOT/contrib/build-wine/dist`.
+
+
+
+Note: the `setup` binary (NSIS installer) is not deterministic yet.