Add tests for building applications using arrow with different feature flags

[alamb]

Which issue does this PR close?

Re: #529

Rationale for this change

The current CI test (here) to ensure arrow builds with various feature flags did not catch #529. This is because it is run in the context of the overall workspace which does not behave the same way as when arrow is used as a dependency

This PR contains the test strategy I propose to use for testing that arrow properly builds with different options. I plan a follow on PR that actually fixed #529

What changes are included in this PR?

This PR contains the test strategy I propose to use for testing that arrow properly builds with different options. I plan a follow on PR that actually fixed #529

Changes

1. Create actual projects that specify arrow as a dependency with various flags
2. Try to build that project in CI

Here is an example of the test running on CI: https://github.com/apache/arrow-rs/runs/3032269357?check_suite_focus=true (it is quite fast to check the projects)

You easily run these builds locally:

cd arrow/test/dependency/no-features
cargo check

I am sure there is some clever tool somewhere that claims to solve this problem (perhaps cargo hack? as suggested by @ritchie46). However, I chose to do it explicitly here because:

1. It is as close as possible to how an actual user will build their app with arrow
2. I can audit how it works without having to review projects and asses how mature / stable they are

Are there any user-facing changes?

no

[alamb]

When this line is removed the test fails. I will remove it with the fix for #529

[codecov-commenter]

Codecov Report

Merging #532 (c1b5fa6) into master (f1fb2b1) will not change coverage.
The diff coverage is n/a.

❗ Current head c1b5fa6 differs from pull request most recent head 65db5ad. Consider uploading reports for the commit 65db5ad to get more accurate results

@@           Coverage Diff           @@
##           master     #532   +/-   ##
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  Coverage   82.60%   82.60%           
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  Files         167      167           
  Lines       45984    45984           
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  Hits        37984    37984           
  Misses       8000     8000           

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[nevi-me]

I think this strategy is sound, LGTM

[nevi-me]

stray line?

[alamb]

Actually, this is required (you get a cargo build error without it). Somehow this signals to cargo that this project is not part of the workspace rooted at arrow-rs/Cargo.toml

[nevi-me]

Could this be what was missing ito catching other feature types? That we weren't running cargo check --all-targets --features simd,...

[alamb]

I think the reason CI isn't catching issues with feature flags is due to the cargo semantics of a workspace -- where Cargo tries to calculate the dependency needs of the workspace as a whole. Since we have some crates in the workspace (like arrow-flight) that bring in additional dependencies, these additional dependencies can obscure build problems with other crates (like arrow) when used alone