Issue #28066: Fix include search directory logic for out-of-tree builds

Misc/NEWS

@@ -322,6 +322,9 @@ Windows
 Build
 -----
 
+- Issue #28066: Fix the logic that searches build directories for generated
+  include files when building outside the source tree.
+
 - Issue #27566: Fix clean target in freeze makefile (patch by Lisa Roach)
 
 - Issue #27705: Update message in validate_ucrtbase.py

configure

@@ -2820,7 +2820,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
 
-if test "$abs_srcdir" != "$abs_builddir"; then
+if test "$srcdir" != . -a "$srcdir" != "$(pwd)"; 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

configure.ac

@@ -10,7 +10,7 @@ AC_PREREQ(2.65)
 AC_INIT(python, PYTHON_VERSION, https://bugs.python.org/)
 
 AC_SUBST(BASECPPFLAGS)
-if test "$abs_srcdir" != "$abs_builddir"; then
+if test "$srcdir" != . -a "$srcdir" != "$(pwd)"; 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