Add _Concurrency module.

This is an empty module that silences compiler warnings.

Author: zoecarver

Sources/CMakeLists.txt

@@ -8,3 +8,4 @@ SPDX-License-Identifier: BSD-3
 add_subdirectory(Runtime)
 add_subdirectory(Core)
 add_subdirectory(Onone)
+add_subdirectory(_Concurrency)

Sources/_Concurrency/CMakeLists.txt

@@ -0,0 +1,19 @@
+#[[
+Copyright © 2018 Saleem Abdulrasool <[email protected]>.
+All Rights Reserved.
+
+SPDX-License-Identifier: BSD-3
+#]]
+
+add_library(swift_Concurrency
+  _Concurrency.swift)
+set_target_properties(swift_Concurrency PROPERTIES
+  Swift_MODULE_NAME _Concurrency)
+target_compile_options(swift_Concurrency PRIVATE
+  -parse-stdlib
+  -disallow-use-new-driver
+  "SHELL:-Xfrontend -enable-resilience")
+target_link_libraries(swift_Concurrency PUBLIC
+  swiftCore)
+target_link_options(swift_Concurrency PRIVATE
+  "SHELL:-Xclang-linker -nostdlib")