xcodebackend: Undefined variable 'MesonException'

E:430,22: Undefined variable 'MesonException' (undefined-variable)

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>

xcodebackend.py

@@ -16,6 +16,8 @@ import backends, build
 import mesonlib
 import uuid, os, sys
 
+from coredata import MesonException
+
 class XCodeBackend(backends.Backend):
     def __init__(self, build, interp):
         super().__init__(build, interp)