         self.swiftCompiler = swiftCompilers.compile
 
         // Look for llbuild in bin dir.
-        llbuild = binDir.appending(component: "swift-build-tool")
+        llbuild = binDir.appending(component: "swift-build-tool" + hostExecutableSuffix)
         guard localFileSystem.exists(llbuild) else {
             throw InvalidToolchainDiagnostic("could not find `llbuild` at expected path \(llbuild)")
         }


    /// 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.
