cranelift: add i64.{ishl,ushr,ashr} libcalls.

These libcalls are useful for 32-bit platforms.

On x86_32 in particular, commit 4ec16fa0 added support for legalizing
64-bit shifts through SIMD operations. However, that legalization
requires SIMD to be enabled and SSE 4.1 to be supported, which is not
acceptable as a hard requirement.

crates/jit/src/link.rs

@@ -50,6 +50,9 @@ fn apply_reloc(
                 SdivI64 => wasmtime_i64_sdiv as usize,
                 UremI64 => wasmtime_i64_urem as usize,
                 SremI64 => wasmtime_i64_srem as usize,
+                IshlI64 => wasmtime_i64_ishl as usize,
+                UshrI64 => wasmtime_i64_ushr as usize,
+                SshrI64 => wasmtime_i64_sshr as usize,
                 CeilF32 => wasmtime_f32_ceil as usize,
                 FloorF32 => wasmtime_f32_floor as usize,
                 TruncF32 => wasmtime_f32_trunc as usize,