[lld] [lld][WebAssembly] Fix check for implicitly exported mutable globals (PR #160966)

[Derek Schuff via llvm-commits]

https://github.com/dschuff approved this pull request.

I guess the stack pointer is very rarely used outside of the module, and EXPORT_ALL is also uncommon, so nobody noticed.

https://github.com/llvm/llvm-project/pull/160966