Guard realpath usage against use on nonexistant paths

[weswigham]

To test if this is a possible fix for #46204

[weswigham]

@typescript-bot pack this

[typescript-bot]

Heya @weswigham, I've started to run the tarball bundle task on this PR at e0f7793. You can monitor the build here.

[typescript-bot]

Hey @weswigham, I've packed this into an installable tgz. You can install it for testing by referencing it in your package.json like so:

{
    "devDependencies": {
        "typescript": "https://typescript.visualstudio.com/cf7ac146-d525-443c-b23c-0d58337efebc/_apis/build/builds/112407/artifacts?artifactName=tgz&fileId=8F1FF35FE0E25412F3B569B456232CF3A2E457062BFE03921A9BDE153E7F5E0802&fileName=/typescript-4.5.0-insiders.20211004.tgz"
    }
}

and then running npm install.

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There is also a playground for this build and an npm module you can use via "typescript": "npm:@typescript-deploys/pr-build@4.5.0-pr-46208-2".;