Add ccache

Author: tvami

Dockerfile

@@ -19,6 +19,7 @@ RUN chmod +x /usr/local/bin/install-ubuntu-packages
 # Basic OS/System tools
 RUN install-ubuntu-packages \
     binutils \
+    ccache \
     cmake \
     gcc g++ gfortran \
     libcurl4-openssl-dev \

docs/src/ubuntu-packages.md

@@ -36,6 +36,7 @@ awk -f docs/src/get-ubuntu-packages.awk Dockerfile
 Package | Reason
 ---|---
 binutils | Adding PPA and linking libraries
+ccache | Improve compilation of ldmx-sw 
 cmake | Configuration of build system
 gcc | GNU C Compiler
 g++ | GNU C++ Compiler