Add Dockerfile that allows cross compiling the client

.gitignore

@@ -7,7 +7,6 @@ CMakeLists.txt.user*
 doc/_build/*
 *.kate-swp
 *.kdev4
-win/
 admin/win/nsi/l10n/pofiles/*.po
 *.swp
 *~$

admin/win/docker/Dockerfile

@@ -0,0 +1,37 @@
+FROM opensuse:42.1
+
+MAINTAINER Daniel Molkentin <danimo@owncloud.com>
+
+ENV TERM ansi
+ENV HOME /root
+
+ENV REFRESHED_AT 20160202
+
+RUN zypper --non-interactive --gpg-auto-import-keys refresh
+RUN zypper --non-interactive --gpg-auto-import-keys ar http://download.opensuse.org/repositories/windows:/mingw/openSUSE_42.1/windows:mingw.repo
+RUN zypper --non-interactive --gpg-auto-import-keys ar http://download.opensuse.org/repositories/isv:ownCloud:toolchains:mingw:win32:2.1/openSUSE_Leap_42.1/isv:ownCloud:toolchains:mingw:win32:2.1.repo
+RUN zypper --non-interactive --gpg-auto-import-keys install cmake make mingw32-cross-binutils mingw32-cross-cpp mingw32-cross-gcc \
+                      mingw32-cross-gcc-c++ mingw32-cross-pkg-config mingw32-filesystem \
+                      mingw32-headers mingw32-runtime site-config mingw32-libwebp \
+                      mingw32-cross-libqt5-qmake mingw32-cross-libqt5-qttools mingw32-libqt5* \
+                      mingw32-qt5keychain* mingw32-angleproject* \
+                      mingw32-cross-nsis mingw32-libopenssl* \
+                      mingw32-sqlite* kdewin-png2ico \
+                      osslsigncode wget
+
+# RPM depends on curl for installs from HTTP
+RUN zypper --non-interactive --gpg-auto-import-keys install curl
+
+# sudo needed for building as user
+RUN zypper --non-interactive --gpg-auto-import-keys install sudo
+
+# Use packaged UAC dependencies
+RUN zypper --non-interactive --gpg-auto-import-keys install mingw32-cross-nsis-plugin-uac mingw32-cross-nsis-plugin-nsprocess
+
+# Required for checksumming
+RUN zypper --non-interactive --gpg-auto-import-keys install mingw32-zlib-devel
+
+# Required for windres not to crash
+RUN zypper --non-interactive --gpg-auto-import-keys install glibc-locale
+
+CMD /bin/bash