[PATCH] autoconf: fix handling absolute $PYTHON path

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

Don't strip full path from $PYTHON variable. This is especially
relevant, if it points outside of $PATH. This is the case
for RPM build on CentOS 8 (%{python3} macro points at
/usr/libexec/platform-python).

For this reason, adjust also python-config handling - AC_PATH_PROG
doesn't work on already absolute path, so make it conditional.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
 m4/python_devel.m4 | 6 +++++-
 tools/configure.ac | 1 -
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/m4/python_devel.m4 b/m4/python_devel.m4
index bbf1e0354b2b..676489b8e978 100644
--- a/m4/python_devel.m4
+++ b/m4/python_devel.m4
@@ -2,7 +2,11 @@ AC_DEFUN([AX_CHECK_PYTHON_DEVEL], [
 ac_previous_cppflags=$CPPFLAGS
 ac_previous_ldflags=$LDFLAGS
 ac_previous_libs=$LIBS
-AC_PATH_PROG([pyconfig], [$PYTHON-config], [no])
+AS_IF([echo "$PYTHON" | grep -q "^/"], [
+    pyconfig="$PYTHON-config"
+], [
+    AC_PATH_PROG([pyconfig], [$PYTHON-config], [no])
+])
 AS_IF([test x"$pyconfig" = x"no"], [
     dnl For those that don't have python-config
     CPPFLAGS="$CFLAGS `$PYTHON -c 'import distutils.sysconfig; \
diff --git a/tools/configure.ac b/tools/configure.ac
index 6414fcbb445e..ebf1265643b3 100644
--- a/tools/configure.ac
+++ b/tools/configure.ac
@@ -368,7 +368,6 @@ AS_IF([test -z "$PYTHON"], [AC_CHECK_PROGS([PYTHON], [python3 python python2], e
 AS_IF([test "$PYTHON" = "err"], [AC_MSG_ERROR([No python interpreter found])])
 AS_IF([echo "$PYTHON" | grep -q "^/"], [], [AC_PATH_PROG([PYTHON], [$PYTHON])])
 PYTHONPATH=$PYTHON
-PYTHON=`basename $PYTHONPATH`
 
 AX_PATH_PROG_OR_FAIL([PYTHONPATH], [$PYTHON])
 AX_CHECK_PYTHON_VERSION([2], [6])
-- 
2.26.3