Port GrMemoryPool emscripten alignment fix to SkSL::MemoryPool

Bug: b/298303571
Change-Id: I60f92c703e81da52f5d9178d24992be5d3952dee
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/751522
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
4 files changed