tools build: Allow deferring printing the results of feature detection

By setting FEATURE_DISPLAY_DEFERRED=1 a tool may ask for the printout
of the detected features in tools/build/Makefile.feature to be done
later adter extra feature checks are done that are tool specific.

The perf tool will do it via its tools/perf/Makefile.config, as it
performs such extra feature checks.

Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/build/Makefile.feature

@@ -240,17 +240,24 @@ ifeq ($(VF),1)
   feature_verbose := 1
 endif
 
-ifeq ($(feature_display),1)
+feature_display_entries = $(eval $(feature_display_entries_code))
-  $(info )
+define feature_display_entries_code
-  $(info Auto-detecting system features:)
+  ifeq ($(feature_display),1)
-  $(foreach feat,$(FEATURE_DISPLAY),$(call feature_print_status,$(feat),))
+    $(info )
-  ifneq ($(feature_verbose),1)
+    $(info Auto-detecting system features:)
+    $(foreach feat,$(FEATURE_DISPLAY),$(call feature_print_status,$(feat),))
+    ifneq ($(feature_verbose),1)
+      $(info )
+    endif
+  endif
+
+  ifeq ($(feature_verbose),1)
+    TMP := $(filter-out $(FEATURE_DISPLAY),$(FEATURE_TESTS))
+    $(foreach feat,$(TMP),$(call feature_print_status,$(feat),))
     $(info )
   endif
-endif
+endef
 
-ifeq ($(feature_verbose),1)
+ifeq ($(FEATURE_DISPLAY_DEFERRED),)
-  TMP := $(filter-out $(FEATURE_DISPLAY),$(FEATURE_TESTS))
+  $(call feature_display_entries)
-  $(foreach feat,$(TMP),$(call feature_print_status,$(feat),))
-  $(info )
 endif