linker: ignore the possibility of page size migration for 32-bit processes.

There's no reason for a 32-bit process to waste time checking this or
looking for the corresponding ELF notes, since this is a 64-bit feature.

Bug: https://issuetracker.google.com/380356872
Change-Id: I4fe6cf478ebd7d2d0ac7e1c3a4eceb0a3fa08e2d
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index 14bf208..e5369ac 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -752,9 +752,10 @@
 }
 
 /*
- * Returns true if the kernel supports page size migration, else false.
+ * Returns true if the kernel supports page size migration for this process.
  */
 bool page_size_migration_supported() {
+#if defined(__LP64__)
   static bool pgsize_migration_enabled = []() {
     std::string enabled;
     if (!android::base::ReadFileToString("/sys/kernel/mm/pgsize_migration/enabled", &enabled)) {
@@ -763,6 +764,9 @@
     return enabled.find("1") != std::string::npos;
   }();
   return pgsize_migration_enabled;
+#else
+  return false;
+#endif
 }
 
 // Find the ELF note of type NT_ANDROID_TYPE_PAD_SEGMENT and check that the desc value is 1.