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 <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/config/Makefile

···
 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
···
   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

tools/perf/util/vdso.c

···
 	enum dso_type dso_type;
 
 	dso_type = machine__thread_dso_type(machine, thread);
+
+#ifndef HAVE_PERF_READ_VDSO32
+	if (dso_type == DSO__TYPE_32BIT)
+		return 0;
+#endif
+#ifndef HAVE_PERF_READ_VDSOX32
+	if (dso_type == DSO__TYPE_X32BIT)
+		return 0;
+#endif
+
 	switch (dso_type) {
 	case DSO__TYPE_32BIT:
 		*dso = vdso__findnew_compat(machine, &vdso_info->vdso32);