fix building sip

Author: 3nids

.docker/qgis3-build-deps.dockerfile

@@ -102,7 +102,7 @@ RUN curl -s -S -O https://www.riverbankcomputing.com/hg/sip/archive/tip.tar.gz \
  && tar xzf tip.tar.gz \
  && bash -c "mv $(ls sip-*) sip-419"
 WORKDIR /root/sip-419
-RUN python3 configure.py && make && make install
+RUN python3 build.py prepare && ython3 configure.py && make && make install
 
 RUN echo "alias python=python3" >> ~/.bash_aliases