[Concurrency] Fix minimal stdlib build again.

Some mentions of `ExecutorJob` were not guarded by the required
`SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY` condition.

Author: al45tair

stdlib/public/Concurrency/Clock.swift

@@ -77,6 +77,7 @@ public protocol Clock<Duration>: Sendable {
 #endif
 }
 
+#if !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
 extension Clock {
   // The default implementation works by creating a trampoline and calling
   // the run() method.
@@ -96,6 +97,7 @@ extension Clock {
     fatalError("\(Self.self) does not implement run(_:at:tolerance:).")
   }
 }
+#endif // !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
 
 @available(StdlibDeploymentTarget 5.7, *)
 extension Clock {

stdlib/public/Concurrency/ContinuousClock.swift

@@ -212,7 +212,7 @@ extension ContinuousClock.Instant: InstantProtocol {
   }
 }
 
-#if !$Embedded
+#if !$Embedded && !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
 @available(StdlibDeploymentTarget 6.2, *)
 extension ContinuousClock {
 

stdlib/public/Concurrency/ExecutorImpl.swift

@@ -47,7 +47,7 @@ internal func donateToGlobalExecutor(
 @available(SwiftStdlib 6.2, *)
 @_silgen_name("swift_task_getMainExecutorImpl")
 internal func getMainExecutor() -> UnownedSerialExecutor {
-  return _getMainExecutorAsSerialExecutor()
+  return unsafe _getMainExecutorAsSerialExecutor()
 }
 
 @available(SwiftStdlib 6.2, *)

stdlib/public/Concurrency/SuspendingClock.swift

@@ -190,7 +190,7 @@ extension SuspendingClock.Instant: InstantProtocol {
   }
 }
 
-#if !$Embedded
+#if !$Embedded && !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
 @available(StdlibDeploymentTarget 6.2, *)
 extension SuspendingClock {