Slim down static binaries by avoiding stdio.

It's okay for a program to choose to drag in stdio, but it's unfortunate
if even the minimal "int main() { return 42; }" drags in stdio...

This brings the minimal static binary on ARM down from 78KiB to 46KiB.

Given that we don't have a separate -lpthread it's not obvious to me that
we can shave this down any further. I'm not sure whether this is a worthwhile
change for that reason. (And the fact that dynamic binaries, the usual case,
are unaffected either way.)

Change-Id: I02f91dcff37d14354314a30b72fed2563f431c88

libc/bionic/jemalloc_wrapper.cpp

@@ -21,7 +21,7 @@
 #include "private/bionic_macros.h"
 
 void* je_pvalloc(size_t bytes) {
-  size_t pagesize = sysconf(_SC_PAGESIZE);
+  size_t pagesize = getpagesize();
   size_t size = BIONIC_ALIGN(bytes, pagesize);
   if (size < bytes) {
     return NULL;