closes bpo-34212: Build core extension modules with Py_BUILD_CORE_BUILTIN. (GH-8712)

Makefile.pre.in

@@ -106,6 +106,7 @@ ARFLAGS=	@ARFLAGS@
 CFLAGSFORSHARED=@CFLAGSFORSHARED@
 # C flags used for building the interpreter object files
 PY_STDMODULE_CFLAGS= $(PY_CFLAGS) $(PY_CFLAGS_NODIST) $(PY_CPPFLAGS) $(CFLAGSFORSHARED)
+PY_BUILTIN_MODULE_CFLAGS= $(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN
 PY_CORE_CFLAGS=	$(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE
 # Strict or non-strict aliasing flags used to compile dtoa.c, see above
 CFLAGS_ALIASING=@CFLAGS_ALIASING@

Modules/makesetup

@@ -233,7 +233,7 @@ sed -e 's/[ 	]*#.*//' -e '/^[ 	]*$/d' |
 			case $doconfig in
 			no)	cc="$cc \$(CCSHARED) \$(PY_CFLAGS) \$(PY_CPPFLAGS)";;
 			*)
-				cc="$cc \$(PY_STDMODULE_CFLAGS)";;
+				cc="$cc \$(PY_BUILTIN_MODULE_CFLAGS)";;
 			esac
 			rule="$obj: $src; $cc $cpps -c $src -o $obj"
 			echo "$rule" >>$rulesf