[fuchsia] Use sysconf to get number of processors

runtime/bin/platform_fuchsia.cc

Index: runtime/bin/platform_fuchsia.cc
diff --git a/runtime/bin/platform_fuchsia.cc b/runtime/bin/platform_fuchsia.cc
index 198521b84e2da0fed6ab91b4525f267fbfb9f616..3e636d1e1c74ef3406b800a27c78ffa673c4a97d 100644
--- a/runtime/bin/platform_fuchsia.cc
+++ b/runtime/bin/platform_fuchsia.cc
@@ -7,7 +7,6 @@
 
 #include "bin/platform.h"
 
-#include <runtime/sysinfo.h>
 #include <string.h>  // NOLINT
 #include <unistd.h>  // NOLINT
 
@@ -28,7 +27,7 @@ bool Platform::Initialize() {
 
 
 int Platform::NumberOfProcessors() {
-  return mxr_get_nprocs_conf();
+  return sysconf(_SC_NPROCESSORS_CONF);
 }