add etc in post

recipes/analysis-suites/deeptools/Singularity.deeptools-351

 Bootstrap: docker
-From: globusgenomics/deeptools:3.5.0--py_0
+From: quay.io/biocontainers/deeptools:3.5.1--py_0
 
 %runscript
-    echo "Running container globusgenomics/deeptools:3.5.1--py_0, deeptools v3.5.1"
+    echo "Running container quay.io/biocontainers/deeptools:3.5.1--py_0, deeptools v3.5.1"
     exec /bin/bash "$@"
 
 %post
-    mkdir /cluster /work /tsd /projects
+    mkdir /cluster /work /tsd /projects /etc
 
 %labels
     Author Nicolas Descostes