Configure the SwiftLint build phase to explicitly run on every build

[mokagio]

Description

Addresses this warning:

We should be running SwiftLint on every build.

Testing instructions

Checkout this branch, build, and verify the warning is gone.

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

You can test the changes from this Pull Request by:

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• Then installing the build number pr8098-5d32126 on your iPhone

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[jkmassel]

Do we want this? For instance, if I change the README should it re-run SwiftLint?

Can we do something with input files like *.swift that only runs if a Swift file is changed? Just slightly more efficient IMHO

[mokagio]

Oh yes, good point. 🤔 I'm sure there's a pattern we can use in the Xcode UI list or .xcfilelist to get there.

[mokagio]

@jkmassel I've been playing with the options here.

To get the full advantage of having the input file list, we also need an output file. In the case of a build phase that runs SwiftLint, that would have to be a dummy file, see #8134.

This screenshot shows the error one gets with "Based on dependency analysis" checked but no output files:

I worry a setup with a dummy output file would end up being more confusing than useful. In particular when we consider:

• Running SwiftLint doesn't take long (*)
• It seems reasonable to assume most builds run on a project like this one will include changes to Swift files

* here's a quick test I run on my Apple M1 Max 32 GB machine, showing SwiftLint taking < 0.2s on average:

➜ time ./Scripts/build-phases/swiftlint.sh
...
./Scripts/build-phases/swiftlint.sh  0.05s user 0.12s system 144% cpu 0.115 total

➜ time ./Scripts/build-phases/swiftlint.sh
...
./Scripts/build-phases/swiftlint.sh  0.05s user 0.12s system 143% cpu 0.117 total

➜ time ./Scripts/build-phases/swiftlint.sh
...
./Scripts/build-phases/swiftlint.sh  0.04s user 0.11s system 143% cpu 0.108 total