[Concurrency] Remove libatomic dependency on Concurrency module on Linux

Author: drexin

stdlib/public/Concurrency/CMakeLists.txt

@@ -33,8 +33,7 @@ endif()
 # Frustratingly, in many cases this isn't necessary because the
 # sequence is inlined, but we have some code that's just subtle
 # enough to turn into runtime calls.
-if(SWIFT_HOST_VARIANT STREQUAL "linux" OR
-   SWIFT_HOST_VARIANT STREQUAL "android")
+if(SWIFT_HOST_VARIANT STREQUAL "android")
   list(APPEND SWIFT_RUNTIME_CONCURRENCY_SWIFT_LINK_FLAGS
     -latomic)
 endif()

stdlib/public/Concurrency/TaskPrivate.h

@@ -159,7 +159,7 @@ class TaskFutureWaitAsyncContext : public AsyncContext {
 } // end anonymous namespace
 
 /// The current state of a task's status records.
-class ActiveTaskStatus {
+class alignas(sizeof(void*) * 2) ActiveTaskStatus {
   enum : uintptr_t {
     /// The current running priority of the task.
     PriorityMask = 0xFF,