Issue #15819: use standard autoconf preset output variables.
Reported by: Roumen Petrov
diff --git a/configure.ac b/configure.ac
index 04413e9..4eb6c43 100644
--- a/configure.ac
+++ b/configure.ac
@@ -9,10 +9,8 @@
AC_INIT(python, PYTHON_VERSION, http://bugs.python.org/)
-BUILDDIR="`pwd`"
-AC_SUBST(BUILDDIR)
AC_SUBST(BASECPPFLAGS)
-if test "$srcdir" != "." -a "$srcdir" != "$BUILDDIR"; then
+if test "$abs_srcdir" != "$abs_builddir"; then
# If we're building out-of-tree, we need to make sure the following
# resources get picked up before their $srcdir counterparts.
# Objects/ -> typeslots.inc