Potential fix for --xcode build on M1.

Author: johnno1962

SwiftCompilerSources/CMakeLists.txt

@@ -171,7 +171,7 @@ function(add_swift_compiler_modules_library name)
   endforeach()
 
   # Create a static library containing all module object files.
-  add_library(${name} STATIC ${all_obj_files})
+  add_library(${name} STATIC force_lib.c ${all_obj_files})
   add_dependencies(${name} ${all_module_targets})
   set_target_properties(${name} PROPERTIES LINKER_LANGUAGE CXX)
   set_property(GLOBAL APPEND PROPERTY SWIFT_BUILDTREE_EXPORTS ${name})

SwiftCompilerSources/force_lib.c

@@ -0,0 +1,14 @@
+//===--- force_lib.c ------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+/// Dummy source file to force CMake generated SwiftInTheCompiler.xcodeproj to sucessfully build static
+/// libraries containing only object fies for "bootstrap" process building Swift sources into compiler.