Update Dockerfile

windows/Dockerfile

@@ -18,6 +18,7 @@ git clone https://github.com/mxe/mxe.git && \
 cd mxe && \
 NPROC=$(($(grep -c ^processor /proc/cpuinfo 2>/dev/null || 1)+4)) && \
 make --jobs=$NPROC JOBS=$NPROC MXE_TARGETS='i686-w64-mingw32.static' qtbase qtmultimedia && \
-/opt/mxe/usr/bin/i686-w64-mingw32.static-qmake-qt5 --version && \
+ln -s /opt/mxe/usr/bin/i686-w64-mingw32.static-qmake-qt5 /usr/bin/qmake && \
+qmake --version && \
 exit 0
 ENV PATH="${PATH}:/opt/mxe/usr/bin"