boost 1.71.0 can't be compiled with mingw

bootstrap.bat gcc #come from E:\MinGW\bin
Building Boost.Build engine
builtins.cpp: In function 'FILE* windows_popen_wrapper(const char*, const char*)':
builtins.cpp:2483:39: error: '_popen' was not declared in this scope
result = _popen( command, "r" );
^
builtins.cpp: In function 'LIST* builtin_shell(FRAME*, int)':
builtins.cpp:2549:29: error: '_pclose' was not declared in this scope
exit_status = pclose( p );
...

1.70.0 is okay.

Start with bootstrap.bat and the Boost.Build engine build that fails in builtins.cpp, especially the reported lines 2483 and 2549. Compare the MinGW build behavior between Boost 1.70.0 and 1.71.0, then verify that the engine compiles successfully with the reported setup.

Written by the indexing model from the issue text.