download and build boost if necessary

[threaderic]

hello Alan! Thanks for this useful app.

As I used your program, I met two minors issues solved by this pull request:

• update CmakeLists.txt: if Boost library not found or Version < 1.78.0 fetch and install Version 1.81.0
• fix minor bug to avoid printing help arguments twice

[alandefreitas]

Thanks. To be honest, 1.78.0 is just the version I had at the time. If you want you can even test it to see how low this can go.

In your set(BOOST_INCLUDE_LIBRARIES filesystem system program_options), I believe we need to list the libraries we use, such as process and asio to let the Boost script figure out the dependencies.

[alandefreitas]

Is it good to go?

[threaderic]

I tested it on Linux and it works well.

[alandefreitas]

Okie dokie!

Thanks!