Use correct builtin for discarding task group creation in gyb file

Author: ktoso

stdlib/public/Concurrency/TaskGroup+addTask.swift.gyb

@@ -143,6 +143,12 @@ import Swift
 % HAS_TASK_EXECUTOR = any('taskExecutor:' in param for param in PARAMS)
 %
 % ARROW_RETURN_TYPE = "-> Bool " if IS_ADD_UNLESS_CANCELLED else ""
+%
+% if IS_DISCARDING:
+%   TASK_CREATE_FN = 'Builtin.createDiscardingTask'
+% else:
+%   TASK_CREATE_FN = 'Builtin.createTask'
+% end
 
 % if IFDEF:
 #if ${IFDEF}
@@ -240,7 +246,7 @@ extension ${TYPE} {
     if var name {
       task =
         name.withUTF8 { nameBytes in
-          Builtin.createTask(
+          ${TASK_CREATE_FN}(
             flags: flags,
             initialSerialExecutor: builtinSerialExecutor,
             taskGroup: _group,
@@ -256,7 +262,7 @@ extension ${TYPE} {
     % if HAS_TASK_EXECUTOR:
     if task == nil, let taskExecutor {
       #if $BuiltinCreateAsyncTaskOwnedTaskExecutor
-      task = Builtin.createTask(
+      task = ${TASK_CREATE_FN}(
         flags: flags,
         initialSerialExecutor: builtinSerialExecutor,
         taskGroup: _group,
@@ -267,7 +273,7 @@ extension ${TYPE} {
       let executorBuiltin: Builtin.Executor =
         taskExecutor.asUnownedTaskExecutor().executor
 
-      task = Builtin.createTask(
+      task = ${TASK_CREATE_FN}(
         flags: flags,
         initialSerialExecutor: builtinSerialExecutor,
         taskGroup: _group,
@@ -279,7 +285,7 @@ extension ${TYPE} {
 
     % # The baseline fallback, if no other create calls could be used
     if task == nil {
-      task = Builtin.createTask(
+      task = ${TASK_CREATE_FN}(
         flags: flags,
         initialSerialExecutor: builtinSerialExecutor,
         taskGroup: _group,
@@ -303,8 +309,3 @@ extension ${TYPE} {
 % end
 % end
 % end
-
-// FIXME: The following sources should be in SourceCompatibilityShims.swift,
-//        but the current build has trouble including the generated gyb sources
-//        such that they are available to the same module. As we move to the
-//        new build style we should resolve this. rdar://145171772