Bug 1426452 - Remove check_top_objdir() call from CompileDB; r=chmanchester

Prior to bug 1224450, CompileDB used data from the Makefiles to generate
the compilation command-lines. Now that the data is derived entirely
from moz.build, we don't need to check that the Makefile is present.
This enables a simple "ac_add_options --build-backends=CompileDB"
mozconfig to work without building a make backend first.

MozReview-Commit-ID: 9tYumyUyg5Y

--HG--
extra : rebase_source : 979f729076b3ab4fd719924877b7ef195e34bfd7

python/mozbuild/mozbuild/compilation/database.py

@@ -7,7 +7,6 @@
 import os
 import types
 
-from mozbuild.compilation import util
 from mozbuild.backend.common import CommonBackend
 from mozbuild.frontend.data import (
     ComputedFlags,
@@ -34,8 +33,6 @@ from collections import (
 class CompileDBBackend(CommonBackend):
     def _init(self):
         CommonBackend._init(self)
-        if not util.check_top_objdir(self.environment.topobjdir):
-            raise Exception()
 
         # The database we're going to dump out to.
         self._db = OrderedDict()