[SR-15779] Swift 5.6 nightly build missing the 'index-template.html' file

[heckj]

Previous ID	SR-15779
Radar	None
Original Reporter	@heckj
Type	Bug
Status	Closed
Resolution	Invalid

Environment

```

/Library/Developer/Toolchains/swift-5.6-DEVELOPMENT-SNAPSHOT-2022-01-11-a.xctoolchain/usr/bin/swift --version
Apple Swift version 5.6-dev (LLVM 64a4d678f114158, Swift 8ae983c3480462b)
Target: arm64-apple-macosx12.0

```

Additional Detail from JIRA

Votes	0
Component/s	Swift-DocC
Labels	Bug
Assignee	None
Priority	Medium

md5: c68732becdc37b3ee26d418f6672de64

Issue Description:

I was experimenting with the upcoming static hosting feature for some current documentation, using the Jan 11th 5.6 nightly toolchain `/Library/Developer/Toolchains/swift-5.6-DEVELOPMENT-SNAPSHOT-2022-01-11-a.xctoolchain`

When running `docc convert` to generate a statically hosted site, it's returning the error:
`The directory at '/Library/Developer/Toolchains/swift-5.6-DEVELOPMENT-SNAPSHOT-2022-01-11-a.xctoolchain/usr/share/docc/render' does not contain a valid template. Missing 'index-template.html' file.`

I checked the swift nightly toolchain, and it does have this file, but the latest swift 5.6 nightly doesn't:
```
find /Library/Developer/Toolchains -name "index-template.html"
/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2022-01-09-a.xctoolchain/usr/share/docc/render/index-template.html
```

I suspect that the associated render artifact needs to be regenerated, or a different version included into the toolchain build process. The repository branch for swift-docc-render-artifact does appear to include the file: `https://github.com/apple/swift-docc-render-artifact/tree/release/5.6/dist\`

[heckj]

this ISN'T an issue with the release - I've just finished downloading the release, and the relevant files are in that toolchain setup.

Since it's with an ephemeral toolchain, I'll just close this.

[heckj]

The released swift 5.6 toolchain within Xcode 13.3 beta has the relevant files, and works correctly.