Two separate-but-related questions:

1. How should toolchains like LLVM expose the Wasm page size to source code?

   • WASM_PAGE_SIZE macro?
   • __builtin_wasm_page_size() function?

2. How does this integrate with linkers like lld?

   • Allow each object to specify its own page size; return link errors if they conflict?
   • Disallow each object to specify its own page size; only allow configuring that in the linker?

cc @tlively