Include fixes.

include/boost/process/v2/detail/config.hpp

@@ -19,6 +19,7 @@
 #include <filesystem>
 #include <string_view>
 #include <iomanip>
+#include <optional>
 
 #if defined(ASIO_WINDOWS)
 #define BOOST_PROCESS_V2_WINDOWS 1
@@ -51,6 +52,7 @@
 #include <boost/system/error_code.hpp>
 #include <boost/system/system_category.hpp>
 #include <boost/system/system_error.hpp>
+#include <boost/optional.hpp>
 
 #if defined(BOOST_WINDOWS_API)
 #define BOOST_PROCESS_V2_WINDOWS 1
@@ -72,11 +74,9 @@
 
 #if defined(BOOST_PROCESS_USE_STD_FS)
 #include <filesystem>
-#include <optional>
 #else
 #include <boost/filesystem/path.hpp>
 #include <boost/filesystem/operations.hpp>
-#include <boost/optional.hpp>
 #endif
 
 #define BOOST_PROCESS_V2_BEGIN_NAMESPACE namespace boost { namespace process { namespace v2 {

include/boost/process/v2/posix/bind_fd.hpp

@@ -94,6 +94,7 @@ struct bind_fd
     error_code on_setup(posix::default_launcher & launcher, const filesystem::path &, const char * const *)
     {
         launcher.fd_whitelist.push_back(target);
+        return {};
     }
 
     /// Implementation of the initialization function.

include/boost/process/v2/start_dir.hpp

@@ -11,6 +11,7 @@
 #define BOOST_PROCESS_v2_START_DIR_HPP
 
 #include <boost/process/v2/detail/config.hpp>
+#include <boost/process/v2/detail/last_error.hpp>
 #include <boost/process/v2/default_launcher.hpp>
 
 BOOST_PROCESS_V2_BEGIN_NAMESPACE

include/boost/process/v2/stdio.hpp

@@ -11,6 +11,7 @@
 #define BOOST_PROCESS_V2_STDIO_HPP
 
 #include <boost/process/v2/detail/config.hpp>
+#include <boost/process/v2/detail/last_error.hpp>
 #include <boost/process/v2/default_launcher.hpp>
 #include <cstddef>
 #if defined(BOOST_PROCESS_V2_STANDALONE)