Implement pyconfig.h changes as something to be appended to end.

cpython/Makefile

@@ -89,7 +89,7 @@ $(BUILD)/Makefile: $(BUILD)/.patched $(ZLIBBUILD)/.patched
 
 $(BUILD)/$(LIB): $(BUILD)/Makefile $(HOSTPYTHON) $(HOSTPGEN) Setup.local
 	cp Setup.local $(BUILD)/Modules/
-	cp pyconfig.h $(BUILD)/
+	cat pyconfig.undefs.h >> $(BUILD)/pyconfig.h
 	( \
 		cp build/$(PYVERSION)/host/lib/python$(PYMINOR)/`$(HOSTPYTHON) -c "import sysconfig; print(sysconfig._get_sysconfigdata_name())"`.py build/$(PYVERSION)/Python-$(PYVERSION)/Lib/_sysconfigdata__emscripten_.py; \
 		cd $(BUILD); \

cpython/pyconfig.undefs.h

+#undef HAVE_EPOLL
+#undef HAVE_EPOLL_CREATE1
+#undef HAVE_LINUX_VM_SOCKETS_H
+#undef HAVE_SOCKETPAIR