Fix Issue 22738 - std.file.tempDir adds an addition / even when it already has one

[rikkimax]

Bug https://issues.dlang.org/show_bug.cgi?id=22738

Discovered due to dub CI being broken due to 17488 adding an additional path separator when it can on some platforms already have it at the end.

Workaround to get dub passing CI dlang/dub#2208

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22738	regression	std.file.tempDir adds an addition / even when it already has one

⚠️⚠️⚠️ Warnings ⚠️⚠️⚠️

• Regression or critical bug fixes should always target the stable branch. Learn more about rebasing to stable or the D release process.

To target stable perform these two steps:

1. Rebase your branch to upstream/stable:

git rebase --onto upstream/stable upstream/master

2. Change the base branch of your PR to stable

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#8373"

[rikkimax]

This is a regression against master and not stable. The stable branch doesn't have this code in it, which causes said bug.

#5476

It appears that this particular issue may have been encountered in that PR as well.

[CyberShadow]

• Delphi has IncludeTrailingPathDelimiter, maybe std.path should have an equivalent.
• Consecutive slashes have no effect on Linux, so it's surprising that it was a problem in Dub. Perhaps the Dub breakage is its own bug that needs to be addressed.

LGTM otherwise

[rikkimax]

• Consecutive slashes have no effect on Linux, so it's surprising that it was a problem in Dub. Perhaps the Dub breakage is its own bug that needs to be addressed.

Dub's CI breakage I have resolved (once PR is merged), so at least we can get PR's merging again once that is done.

I'm not sure if it needs further work on dub's side, my main concern was getting CI passing not necessarily cleaning up garbage input.