[C++] Use pre-built toolchain libraries where prudent to speed up CI builds #17126
Description
Our Travis CI builds, particularly the ones including Python, are spending a lot of time rebuilding the thirdparty toolchain. We should limit how many times we build the toolchain to just enough to be confident that it yields a working system
Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm
Note: This issue was originally created as ARROW-1253. Please see the migration documentation for further details.