Docker build fails under Mac OS X

[GastonGonzalez]

Steps to Reproduce

1. Checkout feature/docker branch.

2. Run Docker build script.

$ cd docker
$ ./builddocker.sh 
...
xargs: illegal option -- -
usage: xargs [-0opt] [-E eofstr] [-I replstr [-R replacements]] [-J replstr]
             [-L number] [-n number [-x]] [-P maxprocs] [-s size]
             [utility [argument ...]]
...
Step 8/17 : RUN mkdir -p /usr/local/lib/nodejs     && tar -xJf /app/binaries/node-v10.15.3-linux-x64.tar.xz -C /usr/local/lib/nodejs     && java -version     && echo $PATH     && echo node: $(node -v)     && echo npm: $(npm -v)     && echo npx: $(npx -v)     && apt-get purge -y --auto-remove && rm -rf /var/lib/apt/lists/* && rm -rf /etc/apt/sources.list.d/temp.list;
 ---> Running in e2a4b145a0a3
xz: (stdin): File format not recognized
tar: Child returned status 1
tar: Error is not recoverable: exiting now

[GastonGonzalez]

I resolved several Docker build issues when running the build under OS X with this commit.

1. Fixed the package file copy in fetchfiles.sh to work under Mac OS X. xargs behaves a bit different under OS X.
2. Replaced wget with curl since most Mac OS X systems do not have HTTPS support build into wget.
3. Added support for checking if Node has already been dowloaded to the temporary files directory.

FYI: @reusr1