sanitycheck: allow placing parsetab.py in a custom dir

when running multiple instances of sanitycheck, allow placing the
parsetab.py in a customer location that can be set using an environment
variable.

export PARSETAB_DIR=/tmp/

run sanitycheck and the parsetab.py will be placed in /tmp/.

Fixes #4513

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/scripts/sanity_chk/expr_parser.py b/scripts/sanity_chk/expr_parser.py
index 1436300..575b5c5 100644
--- a/scripts/sanity_chk/expr_parser.py
+++ b/scripts/sanity_chk/expr_parser.py
@@ -164,7 +164,10 @@
     else:
         raise SyntaxError("Unexpected end of expression")
 
-parser = yacc.yacc(debug=0)
+if "PARSETAB_DIR" not in os.environ:
+    parser = yacc.yacc(debug=0)
+else:
+    parser = yacc.yacc(debug=0, outputdir=os.environ["PARSETAB_DIR"])
 
 def ast_sym(ast, env):
     if ast in env: