Automate amalgamation distribution in the tools/build script

[tomghuang]

It is tedious and error prone to manually generate amalgamation distribution in both the .tar.gz and .zip formats. I should be able to generate both formats in the tools/build script.

To generate the .zip file:

$ zip -r argtable-x.x.x-amalgamation.zip dist

To generate the .tar.gz file:

$ tar -cvzf argtable-x.x.x-amalgamation.tar.gz dist

I need to figure out how to get the version number within the tools/build script.