Fix s390x regressions (#3330)

- Add relocation handling needed after PR #3275
- Fix incorrect handling of signed constants detected by PR #3056 test
- Fix LabelUse max pos/neg ranges; fix overflow in buffers.rs
- Disable fuzzing tests that require pre-built v8 binaries
- Disable cranelift test that depends on i128
- Temporarily disable memory64 tests

crates/fuzzing/src/oracles.rs

@@ -21,9 +21,9 @@ use std::time::{Duration, Instant};
 use wasmtime::*;
 use wasmtime_wast::WastContext;
 
-#[cfg(not(windows))]
+#[cfg(not(any(windows, target_arch = "s390x")))]
 pub use v8::*;
-#[cfg(not(windows))]
+#[cfg(not(any(windows, target_arch = "s390x")))]
 mod v8;
 
 static CNT: AtomicUsize = AtomicUsize::new(0);