Bug 1416052 - Move config.guess logic to Python; r=nalexander

Instead of evaluating config.guess in client.mk, we evaluate it
in Python. The Python code also looks for CONFIG_GUESS in the
mozconfig. This still happens in client.mk courtesy of evaling
the mozconfig's relevant parts.

MozReview-Commit-ID: 87NmQiB2ccX

--HG--
extra : rebase_source : 368bc7bf1375a3943ce62fbb77458c40091a7092

client.mk

@@ -34,8 +34,6 @@ endif
 
 PYTHON ?= $(shell which python2.7 > /dev/null 2>&1 && echo python2.7 || echo python)
 
-CONFIG_GUESS := $(shell $(TOPSRCDIR)/build/autoconf/config.guess)
-
 ####################################
 # Load mozconfig Options
 

python/mozbuild/mozbuild/controller/building.py

@@ -1321,6 +1321,8 @@ def _run_client_mk(self, target=None, line_handler=None, jobs=0,
         append_env = dict(append_env or {})
         append_env['TOPSRCDIR'] = self.topsrcdir
 
+        append_env['CONFIG_GUESS'] = self.resolve_config_guess()
+
         return self._run_make(srcdir=True,
                               filename='client.mk',
                               allow_parallel=False,