This patch fixes the following bugs:

[#413582] g++ must be called for c++ extensions
[#454030] distutils cannot link C++ code with GCC

topdir = "Lib/distutils"

* bcppcompiler.py
  (BCPPCompiler.create_static_lib): Fixed prototype, removing extra_preargs
  and extra_postargs parameters. Included target_lang parameter.
  (BCPPCompiler.link): Included target_lang parameter.

* msvccompiler.py
  (MSVCCompiler.create_static_lib): Fixed prototype, removing extra_preargs
  and extra_postargs parameters. Included target_lang parameter.
  (MSVCCompiler.link): Included target_lang parameter.

* ccompiler.py
  (CCompiler): New language_map and language_order attributes, used by
  CCompiler.detect_language().

  (CCompiler.detect_language): New method, will return the language of
  a given source, or list of sources. Individual source language is
  detected using the language_map dict. When mixed sources are used,
  language_order will stablish the language precedence.

  (CCompiler.create_static_lib, CCompiler.link, CCompiler.link_executable,
   CCompiler.link_shared_object, CCompiler.link_shared_lib):
  Inlcuded target_lang parameter.

* cygwinccompiler.py
  (CygwinCCompiler.link): Included target_lang parameter.

* emxccompiler.py
  (EMXCCompiler.link): Included target_lang parameter.

* mwerkscompiler.py
  (MWerksCompiler.link): Included target_lang parameter.

* extension.py
  (Extension.__init__): New 'language' parameter/attribute, initialized
  to None by default. If provided will overlap the automatic detection
  made by CCompiler.detect_language(), in build_ext command.

* sysconfig.py
  (customize_compiler): Check Makefile for CXX option, and also the
  environment variable CXX. Use the resulting value in the 'compiler_cxx'
  parameter of compiler.set_executables().

* unixccompiler.py
  (UnixCCompiler): Included 'compiler_cxx' in executables dict, defaulting
  to 'cc'.
  (UnixCCompiler.create_static_lib): Included target_lang parameter.
  (UnixCCompiler.link): Included target_lang parameter, and made
  linker command use compiler_cxx, if target_lang is 'c++'.

* command/build_ext.py
  (build_ext.build_extension): Pass new ext.language attribute
  to compiler.link_shared_object()'s target_lang parameter. If
  ext.language is not provided, detect language using
  compiler.detect_language(sources) instead.

* command/config.py
  (config._link): Pass already available lang parameter as target_lang
  parameter of compiler.link_executable().

Lib/distutils/command/config.py

@@ -148,7 +148,8 @@ class config (Command):
         prog = os.path.splitext(os.path.basename(src))[0]
         self.compiler.link_executable([obj], prog,
                                       libraries=libraries,
-                                      library_dirs=library_dirs)
+                                      library_dirs=library_dirs,
+                                      target_lang=lang)
 
         prog = prog + self.compiler.exe_extension
         self.temp_files.append(prog)