[libc++] Avoid including <string> in <mutex>

Author: philnik777

libcxx/include/__condition_variable/condition_variable.h

@@ -16,7 +16,7 @@
 #include <__config>
 #include <__mutex/mutex.h>
 #include <__mutex/unique_lock.h>
-#include <__system_error/system_error.h>
+#include <__system_error/throw_system_error.h>
 #include <__thread/support.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_floating_point.h>

libcxx/include/__mutex/unique_lock.h

@@ -14,7 +14,7 @@
 #include <__config>
 #include <__memory/addressof.h>
 #include <__mutex/tag_types.h>
-#include <__system_error/system_error.h>
+#include <__system_error/throw_system_error.h>
 #include <__utility/swap.h>
 #include <cerrno>
 

libcxx/include/__system_error/system_error.h

@@ -39,7 +39,6 @@ class _LIBCPP_EXPORTED_FROM_ABI system_error : public runtime_error {
   _LIBCPP_HIDE_FROM_ABI const error_code& code() const _NOEXCEPT { return __ec_; }
 };
 
-[[__noreturn__]] _LIBCPP_EXPORTED_FROM_ABI void __throw_system_error(int __ev, const char* __what_arg);
 [[__noreturn__]] _LIBCPP_HIDE_FROM_ABI inline void __throw_system_error(error_code __ec, const char* __what_arg) {
 #if _LIBCPP_HAS_EXCEPTIONS
   throw system_error(__ec, __what_arg);

libcxx/include/__system_error/throw_system_error.h

@@ -0,0 +1,25 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___SYSTEM_ERROR_THROW_SYSTEM_ERROR_H
+#define _LIBCPP___SYSTEM_ERROR_THROW_SYSTEM_ERROR_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+[[__noreturn__]] _LIBCPP_EXPORTED_FROM_ABI void __throw_system_error(int __ev, const char* __what_arg);
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___SYSTEM_ERROR_THROW_SYSTEM_ERROR_H