Windows: Consecutive builds fail in Swift 5.10 toolchain

[tishin]

Follow-up to #418. The initial clean build using Swift 5.10 succeeds now, but any build after that fails with:

[0/1] Planning builderror: failed: PrebuildCommand(configuration: SPMBuildCore.BuildToolPluginInvocationResult.CommandConfiguration(displayName: Optional("Generating Swift API from /Projects/SwiftGodot/Sources/ExtensionApi/extension_api.json to /Projects/SwiftGodot/.build/plugins/outputs/swiftgodot/SwiftGodot/CodeGeneratorPlugin/GeneratedSources"), executable: <AbsolutePath:"\Projects\SwiftGodot\.build\plugins\tools\debug\Generator.exe">, arguments: ["/Projects/SwiftGodot/Sources/ExtensionApi/extension_api.json", "/Projects/SwiftGodot/.build/plugins/outputs/swiftgodot/SwiftGodot/CodeGeneratorPlugin/GeneratedSources", "/Projects/SwiftGodot/doc", "--singlefile"], environment: [:], workingDirectory: nil), outputFilesDirectory: <AbsolutePath:"\Projects\SwiftGodot\.build\plugins\outputs\swiftgodot\SwiftGodot\CodeGeneratorPlugin\GeneratedSources">)

Generator/Printer.swift:108: Fatal error: 'try!' expression unexpectedly raised an error: Error Domain=NSCocoaErrorDomain Code=512 "(null)"
Current stack trace:
0    (null)                             0x00007ffe9dae4ae0 swift_stdlib_reportFatalErrorInFile + 132