emscripten: pass --profiling-funcs with --spill-pointers on every version #81

The emscripten toolchain always runs binaryen's --spill-pointers, which needs --profiling-funcs to find the stack pointer, but --profiling-funcs is only added when the detected emscripten major version is 6 or more. Other versions, or a version the detection misreads, fail with "failed to find the stack pointer" or lose GC roots. A define for the wasm stack size would also help with very large generated functions.

Related: HaxeFoundation/hxcpp#987, HaxeFoundation/hxcpp#760, HaxeFoundation/hxcpp#1075.