Windows apps packaging their Swift runtime can make the toolchain unusable

We recently [modified](https://github.com/nicklockwood/SwiftFormat/pull/1830) the installer for Nick Lockwood's SwiftFormat project to include the Swift runtime dlls, since the one installed on the machine might not be ABI-compatible. The installer will add its target folder to the system `%Path%`, which will then win when resolving `swiftCore.dll` and other Swift runtime dlls, breaking the toolchain programs like `swift.exe`. Repro steps: - Install a Swift toolchain different from SwiftFormat's (not 5.10.1) - In a new command prompt, run `swift.exe --version`. It should work as expected. - Install SwiftFormat from [this release](https://github.com/nicklockwood/SwiftFormat/releases/tag/0.54.5) - In a new command prompt, run `swift.exe --version`. It will now crash because it's picking up the Swift runtime binaries from the SwiftFormat installation.