Use an IIFE to scope define:vars scripts

[matthewp]

Changes

• Safari hoists function declarations out of a block scope, https://bugs.webkit.org/show_bug.cgi?id=179698
• This means that our use of block scope breaks any define:vars script (in Safari) that uses a function declaration.
• Part of define:vars not working in Safari astro#5064
• Fix is to use an IIFE instead.

Testing

Tests updated.

Docs

N/A

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🦋 Changeset detected

Latest commit: b225f42

The changes in this PR will be included in the next version bump.

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@astrojs/compiler	Patch

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[tony-sull]

Nice, that fix is a heck of a lot cleaner than I expected given the bug it fixes!

The fix and tests look good to me, leaving it open for Nate's approval though in case there are compiler edge cases hidden here

[natemoo-re]

I was worried about import/export but we're already skipping module scripts, so this looks good!