[llvm] WebAssembly: Move runtime libcall setting out of TargetLowering (PR #142624)

[Matt Arsenault via llvm-commits]

arsenm wrote:

lld/test/wasm/lto/Inputs/libcall-return-addr.ll is failing. This was last moved in #126880, but this is now fixed and there should be no more cases in webassembly. I guess I could port the test to a different target that still has subtarget dependent libcall choices 

https://github.com/llvm/llvm-project/pull/142624