[C++] Do not build unit tests by default?

[asfimport]

This is strictly a subjective call – since more people are using Arrow as a thirdparty library, it might be preferably to only opt-in to running the unit tests (vs. currently: explicitly opting out) for Arrow development.

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

Related issues:

• Arrow 0.3 release (blocks)

_{Note: This issue was originally created as ARROW-859. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
PR: #570

[asfimport]

Uwe Korn / @xhochy:
I'm a bit undecided on this. While compiling unit tests by default makes it easier for potential contributors to spot errors in their contribution, it costs unnecessary compilation time if you only consume arrow.

@wesm What was the motivation for this change? (I probably saw it but can't remember it anymore)

[asfimport]

Wes McKinney / @wesm:
The motivation was simplifying the build for thirdparties somewhat, see e.g. https://github.com/search?utf8=%E2%9C%93&q=-DARROW_BUILD_TESTS%3Doff&type=Code

I don't feel super strongly, so I'm OK with leaving things as they are

[asfimport]

Wes McKinney / @wesm:
resolving as wontfix for now, we can revisit some later time

[asfimport]

Todd Farmer / @toddfarmer:
Transitioning issue from Resolved to Closed to based on resolution field value.