update build scripts to support metadata

[darkn3rd]

Currently dgraph-ratel -version binary does not report any metadata despite code support for metadata. This PR will do the following:

• fix commitID and commitINFO that were set to empty strings
• support passing in commitID, commitINFO, and version externally
• support building building metadata version with docker and make.

Not Goals

The designated key names and value content have not been changed, using it as is. The metadata for commitINFO is bizarre, and I don't understand the original intention for this:

Ratel Version: v21.03.0-16-g5ec15c3
Commit ID: 9debcc4
Commit Info: 9debcc4¨•¨¨•¨Fri¨•¨May¨•¨28¨•¨14:57:46¨•¨2021¨•¨-0700¨•¨¨•¨¨•¨(HEAD¨•¨->¨•¨joaquin/build-meta-update,¨•¨origin/master,¨•¨origin/HEAD,¨•¨master)

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