Fix \n in pip.conf

Author: pandaninjas

Dockerfile

@@ -15,6 +15,5 @@ RUN cd Python-${VERSION} && ./configure && make -j$(nproc) && make install
 
 RUN rm -rf Python-${VERSION} Python-${VERSION}.tgz /etc/apt/sources.list.d/debsrc.list
 
-RUN echo "[global]\
-extra-index-url=https://www.piwheels.org/simple" > /etc/pip.conf 
+RUN echo -e "[global]\nextra-index-url=https://www.piwheels.org/simple" > /etc/pip.conf 
 # replicate raspberry pi os pip.conf