Remove PAGE_SIZE call sites.

To enable experiments with non-4KiB page sizes, introduce
an inline page_size() function that will either return the runtime
page size (if PAGE_SIZE is not 4096) or a constant 4096 (elsewhere).
This should ensure that there are no changes to the generated code on
unaffected platforms.

Test: source build/envsetup.sh
      lunch aosp_cf_arm64_16k_phone-userdebug
      m -j32 installclean
      m -j32
Test: launch_cvd \
  -kernel_path /path/to/out/android14-5.15/dist/Image \
  -initramfs_path /path/to/out/android14-5.15/dist/initramfs.img \
  -userdata_format=ext4
Bug: 277272383
Bug: 230790254
Change-Id: Ic0ed98b67f7c6b845804b90a4e16649f2fc94028
diff --git a/libc/bionic/sysinfo.cpp b/libc/bionic/sysinfo.cpp
index 1e4a0e8..79fd55e 100644
--- a/libc/bionic/sysinfo.cpp
+++ b/libc/bionic/sysinfo.cpp
@@ -33,8 +33,9 @@
 #include <string.h>
 #include <unistd.h>
 
-#include "private/get_cpu_count_from_string.h"
+#include "platform/bionic/page.h"
 #include "private/ScopedReaddir.h"
+#include "private/get_cpu_count_from_string.h"
 
 int __get_cpu_count(const char* sys_file) {
   int cpu_count = 1;
@@ -64,11 +65,11 @@
 long get_phys_pages() {
   struct sysinfo si;
   sysinfo(&si);
-  return (static_cast<int64_t>(si.totalram) * si.mem_unit) / PAGE_SIZE;
+  return (static_cast<int64_t>(si.totalram) * si.mem_unit) / page_size();
 }
 
 long get_avphys_pages() {
   struct sysinfo si;
   sysinfo(&si);
-  return ((static_cast<int64_t>(si.freeram) + si.bufferram) * si.mem_unit) / PAGE_SIZE;
+  return ((static_cast<int64_t>(si.freeram) + si.bufferram) * si.mem_unit) / page_size();
 }