[Gandiva][C++] cast decimal to int should round up

[asfimport]

Reporter: Pindikura Ravindra / @pravindra
Assignee: Pindikura Ravindra / @pravindra

PRs and other links:

• GitHub Pull Request #4864

_{Note: This issue was originally created as ARROW-5925. Please see the migration documentation for further details.}

[asfimport]

Pindikura Ravindra / @pravindra:
Issue resolved by pull request 4864
#4864