Common/MemArena: Add function for getting page size

Source/Core/Common/MemArenaDarwin.cpp

@@ -3,6 +3,8 @@
 
 #include "Common/MemArena.h"
 
+#include <unistd.h>
+
 #include "Common/Assert.h"
 #include "Common/Logging/Log.h"
 
@@ -163,6 +165,11 @@ void MemArena::UnmapFromMemoryRegion(void* view, size_t size)
   }
 }
 
+size_t MemArena::GetPageSize() const
+{
+  return getpagesize();
+}
+
 LazyMemoryRegion::LazyMemoryRegion() = default;
 
 LazyMemoryRegion::~LazyMemoryRegion()