Bug 665407 - Disable sutagent if not building tests. r=ctalbert

build/Makefile.in

@@ -55,6 +55,7 @@ endif
 
 DIRS += pgo
 
+ifdef ENABLE_TESTS
 ifeq (Android,$(OS_TARGET))
   DIRS += mobile/sutagent/android \
           mobile/sutagent/android/watcher \
@@ -62,6 +63,7 @@ ifeq (Android,$(OS_TARGET))
           mobile/sutagent/android/fencp \
           $(NULL)
 endif
+endif
 
 include $(topsrcdir)/config/rules.mk