Update pre_build_script.sh

Author: atalman

packaging/pre_build_script.sh

@@ -37,7 +37,7 @@ else
     conda install -yq ffmpeg=4.2 libjpeg-turbo -c pytorch-nightly
   fi
 
-  conda install -y libwebp ${CONDA_CHANNEL}
+  conda install -v libwebp ${CONDA_CHANNEL}
   conda install libjpeg-turbo -c pytorch
   yum install -y freetype gnutls
   pip install auditwheel