[misc] using mariadb_config from configuration, or if not defined from path

mariadb_posix.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-import os
+import subprocess
 import sys
 
 
@@ -39,8 +39,12 @@ def get_config(options):
     no_env = 0
     static = options["link_static"]
 
-
+    try:
         config_prg = options["mariadb_config"]
+        subprocess.call([config_prg, "--version"])
+    except FileNotFoundError:
+        # using default from path
+        config_prg = "mariadb_config"
 
     cc_version = mariadb_config(config_prg, "cc_version")
     if cc_version[0] < required_version: