VS: Detect compiler component in VS 2017 instances more reliably

The `Microsoft.VisualStudio.Component.VC.Tools.x86.x64` component is
not the only way a VS instance may provide the `cl` compiler tool.
For example, VS 2017 Express Edition does not install that component.
Instead search for the tools directly on disk within an instance.

Suggested-by: Rich Chiodo <rchiodo@microsoft.com>
Fixes: #17349
Status Job ID Name Coverage
  External
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00:21:25

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