perf tools: Do not attempt to run perf-read-vdso32 if it wasn't built

popen() causes an error message to print if perf-read-vdso32 does not
run.  Avoid that by not trying to run it if it was not built.  Ditto
perf-read-vdsox32.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1414061124-26830-17-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
index 3ba2382..71264e4 100644
--- a/tools/perf/config/Makefile
+++ b/tools/perf/config/Makefile
@@ -627,7 +627,9 @@
 ifeq (${IS_64_BIT}, 1)
   ifndef NO_PERF_READ_VDSO32
     $(call feature_check,compile-32)
-    ifneq ($(feature-compile-32), 1)
+    ifeq ($(feature-compile-32), 1)
+      CFLAGS += -DHAVE_PERF_READ_VDSO32
+    else
       NO_PERF_READ_VDSO32 := 1
     endif
   endif
@@ -636,7 +638,9 @@
   endif
   ifndef NO_PERF_READ_VDSOX32
     $(call feature_check,compile-x32)
-    ifneq ($(feature-compile-x32), 1)
+    ifeq ($(feature-compile-x32), 1)
+      CFLAGS += -DHAVE_PERF_READ_VDSOX32
+    else
       NO_PERF_READ_VDSOX32 := 1
     endif
   endif