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ARROW-5776: [Gandiva][Crossbow] Use commit id instead of fetch head.

- It is important to use the same commit to build the various gandiva artifacts
  on OsX/Linux etc, so that they are consistent.
- We use the commit id to pin all of the builds to the same commit on the tree.

Closes #4738 from praveenbingo/ARROW-5776 and squashes the following commits:

05c3888b4 <Pindikura Ravindra> Update array-union-test.cc
94c86fa23 <Praveen> Fix condition.
dc77cdbd8 <Praveen> Suppress mvn output.
6d5238344 <Praveen> Fixed test to compile in manylinux.
bccf49022 <Praveen> Fix java build script.
9d8de1468 <Praveen> Supress all maven output.
3a82c079e <Praveen> Reduce logging, since travis seems to terminate for excessive logging.
12f6c2f14 <Praveen> ARROW-5776:  Add back commit ids instead of fetch head

Lead-authored-by: Praveen <praveen@dremio.com>
Co-authored-by: Pindikura Ravindra <ravindra@dremio.com>
Signed-off-by: Pindikura Ravindra <ravindra@dremio.com>