Mark all closures in the .stream outputRedirection of TSC as @Sendable

The closures aren’t guaranteed to be called on the same thread as the process was launched, which can cause assertion failure by the concurrency runtime.

rdar://142813605

Sources/BuildSystemIntegration/SwiftPMBuildSystem.swift

@@ -655,8 +655,8 @@ package actor SwiftPMBuildSystem: BuiltInBuildSystem {
       arguments: arguments,
       workingDirectory: nil,
       outputRedirection: .stream(
-        stdout: { stdoutHandler.handleDataFromPipe(Data($0)) },
-        stderr: { stderrHandler.handleDataFromPipe(Data($0)) }
+        stdout: { @Sendable bytes in stdoutHandler.handleDataFromPipe(Data(bytes)) },
+        stderr: { @Sendable bytes in stderrHandler.handleDataFromPipe(Data(bytes)) }
       )
     )
     let exitStatus = result.exitStatus.exhaustivelySwitchable