Ignore sysconfig variables for LDCXXSHARED as it appears not to exist on PyPy.

Author: sciyoshi

distutils/sysconfig.py

@@ -300,7 +300,6 @@ def customize_compiler(compiler):  # noqa: C901
             cflags,
             ccshared,
             ldshared,
-            ldcxxshared,
             shlib_suffix,
             ar,
             ar_flags,
@@ -310,13 +309,13 @@ def customize_compiler(compiler):  # noqa: C901
             'CFLAGS',
             'CCSHARED',
             'LDSHARED',
-            'LDCXXSHARED',
             'SHLIB_SUFFIX',
             'AR',
             'ARFLAGS',
         )
 
         cxxflags = cflags
+        ldcxxshared = ""
 
         if 'CC' in os.environ:
             newcc = os.environ['CC']