 private let whichArgs: [String] = ["xcrun", "--find"]
 #else
 private let whichArgs = ["which"]
+#endif
+#if os(Windows)
+private let hostExecutableSuffix = ".exe"
+#else
+private let hostExecutableSuffix = ""
 #endif
 
 /// Concrete object for manifest resource provider.


    /// Path of the `swift` interpreter.
    public var swiftInterpreter: AbsolutePath {
        return swiftCompiler.parentDirectory.appending(component: "swift")
    }

    /// Path to the xctest utility.

        // We require there is at least one valid swift compiler, either in the
        // bin dir or SWIFT_EXEC.
        let resolvedBinDirCompiler: AbsolutePath
        let binDirCompiler = binDir.appending(component: "swiftc" + hostExecutableSuffix)
        if localFileSystem.isExecutableFile(binDirCompiler) {
            resolvedBinDirCompiler = binDirCompiler
        } else if let SWIFT_EXEC = SWIFT_EXEC {
            resolvedBinDirCompiler = SWIFT_EXEC
        } else {
            throw InvalidToolchainDiagnostic("could not find the `swiftc\(hostExecutableSuffix)` at expected path \(binDirCompiler)")
        }

        // The compiler for compilation tasks is SWIFT_EXEC or the bin dir compiler.
