[Debug] Introduce use of DebugDescription macro in stdlib (#71425)

Introduces the first use of `@_DebugDescription` in the standard library, applying it 
to `ObjectIdentifier`. In order to use the DebugDescription macro in the stdlib, the 
following changes are required:

1. Compilation must reference the just built macros (ie `libSwiftMacros.dylib`), not 
those from the SDK. This is addressed by adding an explicit `-external-plugin-path` 
flag that overrides the defaults generated by the compiler (which uses SDK paths, where 
the macro may or may not exist, and may not be the current version).
2. As DebugDescription uses `@_section`, compilation enables the `SymbolLinkageMarkers` 
feature.

Note that the use of DebugDescription is conditionally enabled for the following 
reasons:

1. Use is disabled in freestanding builds, where the stdlib macros are not built.
2. Use is temporarily disabled in Linux builds due to a dynamic loader issue that needs 
further investigation

The dynamic loader error causing issues with Linux CI is:
> swift-plugin-server: error while loading shared libraries: libswiftGlibc.so: cannot 
open shared object file: No such file or directory

This PR depended on #71639, #71588, and #71685.

Author: kastiglione

stdlib/public/core/CMakeLists.txt

@@ -260,6 +260,11 @@ if(SWIFT_STDLIB_ENABLE_VECTOR_TYPES)
   list(APPEND SWIFTLIB_EMBEDDED_GYB_SOURCES SIMDConcreteOperations.swift.gyb SIMDVectorTypes.swift.gyb)
 endif()
 
+# Freestanding and Linux builds both have failures to resolve.
+if(NOT SWIFT_FREESTANDING_FLAVOR AND NOT SWIFT_HOST_VARIANT_SDK STREQUAL "LINUX")
+  list(APPEND SWIFTLIB_SOURCES ObjectIdentifier+DebugDescription.swift)
+endif()
+
 list(APPEND SWIFTLIB_EMBEDDED_SOURCES
   EmbeddedRuntime.swift
   EmbeddedStubs.swift
@@ -310,6 +315,10 @@ list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "Freestand
 list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "Extern")
 list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "BitwiseCopyable")
 
+list(APPEND swift_stdlib_compile_flags "-external-plugin-path"
+  "${CMAKE_BINARY_DIR}/lib/swift/host/plugins#${CMAKE_BINARY_DIR}/bin/swift-plugin-server")
+list(APPEND swift_stdlib_compile_flags "-enable-experimental-feature" "SymbolLinkageMarkers")
+
 set(swift_core_incorporate_object_libraries)
 list(APPEND swift_core_incorporate_object_libraries swiftRuntime)
 list(APPEND swift_core_incorporate_object_libraries swiftLLVMSupport)

stdlib/public/core/DebuggerSupport.swift

@@ -64,13 +64,11 @@ import SwiftShims
 ///   and other arbitrary computation are not supported. Of note, conditional
 ///   logic and computed properties are not supported.
 /// * Overloaded string interpolation cannot be used.
-@available(SwiftStdlib 5.11, *)
 @attached(memberAttribute)
 public macro _DebugDescription() =
   #externalMacro(module: "SwiftMacros", type: "DebugDescriptionMacro")
 
 /// Internal-only macro. See `@_DebugDescription`.
-@available(SwiftStdlib 5.11, *)
 @attached(peer, names: named(_lldb_summary))
 public macro _DebugDescriptionProperty(_ debugIdentifier: String, _ computedProperties: [String]) =
   #externalMacro(module: "SwiftMacros", type: "_DebugDescriptionPropertyMacro")

stdlib/public/core/GroupInfo.json

@@ -161,7 +161,8 @@
     "Mirror.swift",
     "Mirrors.swift",
     "ReflectionMirror.swift",
-    "ObjectIdentifier.swift"
+    "ObjectIdentifier.swift",
+    "ObjectIdentifier+DebugDescription.swift"
   ],
   "Math": [
     "SetAlgebra.swift",

stdlib/public/core/ObjectIdentifier+DebugDescription.swift

@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 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
+//
+//===----------------------------------------------------------------------===//
+
+#if !$Embedded
+@_DebugDescription
+extension ObjectIdentifier {
+  var _debugDescription: String {
+    return "ObjectIdentifier(\(_value))"
+  }
+}
+#endif