Bug 1412460 - Simplify config.guess invocation; r=mshal

The config.guess file is checked into source control. I'm not sure
under what conditions we wouldn't fail to find this file. So the
$(wildcard) shouldn't be necessary.

MozReview-Commit-ID: KCctPFW3Eab

--HG--
extra : rebase_source : 2b9f674bdffc95ac4e1999f9a5d8b7ffa13e8d74

client.mk

@@ -51,11 +51,7 @@ SH := /bin/sh
 PERL ?= perl
 PYTHON ?= $(shell which python2.7 > /dev/null 2>&1 && echo python2.7 || echo python)
 
-CONFIG_GUESS_SCRIPT := $(wildcard $(TOPSRCDIR)/build/autoconf/config.guess)
-ifdef CONFIG_GUESS_SCRIPT
-  CONFIG_GUESS := $(shell $(CONFIG_GUESS_SCRIPT))
-endif
-
+CONFIG_GUESS := $(shell $(TOPSRCDIR)/build/autoconf/config.guess)
 
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 # Sanity checks