[stdlib] Suppress CommandLine : _BitwiseCopyable.

Mark it always unavailable per LWG feedback.

Author: nate-chandler

stdlib/public/core/CommandLine.swift

@@ -61,4 +61,7 @@ public enum CommandLine {
     = (0..<Int(argc)).map { String(cString: _unsafeArgv[$0]!) }
 }
 
+@available(*, unavailable)
+extension CommandLine : _BitwiseCopyable {}
+
 #endif // SWIFT_STDLIB_HAS_COMMANDLINE

test/Sema/bitwise_copyable_2.swift

@@ -36,3 +36,5 @@ func passInternalUsableStruct(_ s: InternalUsableStruct) { take(s) } // expected
                                                                      // expected-note@-8{{where_requirement_failure_one_subst}}
 
 func passMemoryLayout<T>(_ m: MemoryLayout<T>) { take(m) } // expected-error{{conformance_availability_unavailable}}
+
+func passCommandLine(_ m: CommandLine) { take(m) } // expected-error{{conformance_availability_unavailable}}