patch 9.0.1794: autoconf: not correctly detecing include dirs

Problem:  autoconf: not correctly detecing include dirs
Solution: make use of python3 to generate includedirs

configure: Python3: Use sysconfig for -I

It seems better to use tools provided by Python for determining the
include directories, rather than construct them "manually".

Current system is broken when using virtual environments for python
3.11.4.  It used to work before, but now it detects a incorrect value
for `-I`.

It would probably make sense to switch to a similar logic for lib
folders, that is for the `-l` switch.  There are also
`sysconfig.get_config_h_filename()` and
`sysconfig.get_makefile_filename()`, that could replace more Python
specific logic in the current `configure{.ac,}`.

sysconfig provides the necessary tools since Python 2.7.

closes: #12889

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Illia Bobyr <illia.bobyr@gmail.com>

src/auto/configure

@@ -6775,6 +6775,30 @@ fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $vi_cv_path_python3_epfx" >&5
 $as_echo "$vi_cv_path_python3_epfx" >&6; }
 
+            { $as_echo "$as_me:${as_lineno-$LINENO}: checking Python's include path" >&5
+$as_echo_n "checking Python's include path... " >&6; }
+if ${vi_cv_path_python3_include+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+   vi_cv_path_python3_include=`
+       ${vi_cv_path_python3} -c \
+       "import sysconfig; print(sysconfig.get_path(\"include\"))"`
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $vi_cv_path_python3_include" >&5
+$as_echo "$vi_cv_path_python3_include" >&6; }
+
+            { $as_echo "$as_me:${as_lineno-$LINENO}: checking Python's include path" >&5
+$as_echo_n "checking Python's include path... " >&6; }
+if ${vi_cv_path_python3_platinclude+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+   vi_cv_path_python3_platinclude=`
+       ${vi_cv_path_python3} -c \
+       "import sysconfig; print(sysconfig.get_path(\"platinclude\"))"`
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $vi_cv_path_python3_platinclude" >&5
+$as_echo "$vi_cv_path_python3_platinclude" >&6; }
+
 
       if ${vi_cv_path_python3path+:} false; then :
   $as_echo_n "(cached) " >&6
@@ -6873,10 +6897,10 @@ fi
 $as_echo "$vi_cv_dll_name_python3" >&6; }
 
         PYTHON3_LIBS="${vi_cv_path_python3_plibs}"
-        if test "${vi_cv_path_python3_pfx}" = "${vi_cv_path_python3_epfx}"; then
-          PYTHON3_CFLAGS="-I${vi_cv_path_python3_pfx}/include/python${vi_cv_var_python3_version}${vi_cv_var_python3_abiflags}"
+        if test "${vi_cv_path_python3_include}" = "${vi_cv_path_python3_platinclude}"; then
+          PYTHON3_CFLAGS="-I${vi_cv_path_python3_include}"
         else
-          PYTHON3_CFLAGS="-I${vi_cv_path_python3_pfx}/include/python${vi_cv_var_python3_version}${vi_cv_var_python3_abiflags} -I${vi_cv_path_python3_epfx}/include/python${vi_cv_var_python3_version}${vi_cv_var_python3_abiflags}"
+          PYTHON3_CFLAGS="-I${vi_cv_path_python3_include} -I${vi_cv_path_python3_platinclude}"
         fi
         if test "X$have_python3_config_dir" = "X1" -a "$enable_python3interp" = "dynamic"; then
                     PYTHON3_CFLAGS="${PYTHON3_CFLAGS}  -DPYTHON3_HOME='L\"${vi_cv_path_python3_pfx}\"'"

src/configure.ac

@@ -1543,6 +1543,18 @@ if test "$enable_python3interp" = "yes" -o "$enable_python3interp" = "dynamic";
        ${vi_cv_path_python3} -c \
        "import sys; print(sys.exec_prefix)"` ])
 
+      dnl -- python3's include path
+      AC_CACHE_CHECK(Python's include path,vi_cv_path_python3_include,
+      [ vi_cv_path_python3_include=`
+       ${vi_cv_path_python3} -c \
+       "import sysconfig; print(sysconfig.get_path(\"include\"))"` ])
+
+      dnl -- python3's platform include path
+      AC_CACHE_CHECK(Python's include path,vi_cv_path_python3_platinclude,
+      [ vi_cv_path_python3_platinclude=`
+       ${vi_cv_path_python3} -c \
+       "import sysconfig; print(sysconfig.get_path(\"platinclude\"))"` ])
+
       dnl -- python3's internal library path
 
       AC_CACHE_VAL(vi_cv_path_python3path,
@@ -1621,10 +1633,10 @@ eof
 	])
 
         PYTHON3_LIBS="${vi_cv_path_python3_plibs}"
-        if test "${vi_cv_path_python3_pfx}" = "${vi_cv_path_python3_epfx}"; then
-          PYTHON3_CFLAGS="-I${vi_cv_path_python3_pfx}/include/python${vi_cv_var_python3_version}${vi_cv_var_python3_abiflags}"
+        if test "${vi_cv_path_python3_include}" = "${vi_cv_path_python3_platinclude}"; then
+          PYTHON3_CFLAGS="-I${vi_cv_path_python3_include}"
         else
-          PYTHON3_CFLAGS="-I${vi_cv_path_python3_pfx}/include/python${vi_cv_var_python3_version}${vi_cv_var_python3_abiflags} -I${vi_cv_path_python3_epfx}/include/python${vi_cv_var_python3_version}${vi_cv_var_python3_abiflags}"
+          PYTHON3_CFLAGS="-I${vi_cv_path_python3_include} -I${vi_cv_path_python3_platinclude}"
         fi
         if test "X$have_python3_config_dir" = "X1" -a "$enable_python3interp" = "dynamic"; then
           dnl Define PYTHON3_HOME if --with-python-config-dir was used

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1794,
 /**/
     1793,
 /**/