[Halld-offline] new release of Build Scripts, version 2.0

[Mark Ito]

Folks,

This release has two notable new features:

1. Restoration of the run-time tests of the builds initiated by pull 
requests on GitHub (for halld_recon and halld_sim only). The test of 
build itself has always worked. This change restores, for example, a 
short run of halld_root from the build. These kind of tests have not 
been running for a long time now.

2. Compatibility with Python-3-default systems. This was announced a 
week ago, but this feature is now in a tagged release.

Find the release notes for this and the previous (unannounced) release at

   https://github.com/JeffersonLab/build_scripts/releases/tag/1.59

and

   https://github.com/JeffersonLab/build_scripts/releases/tag/2.0

   -- Mark