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/Cargo.toml

@@ -25,8 +25,8 @@ wasmi = "0.7.0"
 # We rely on precompiled v8 binaries, but rusty-v8 doesn't have a precompiled
 # binary for MinGW which is built on our CI. It does have one for Windows-msvc,
 # though, so we could use that if we wanted. For now though just simplify a bit
-# and don't depend on this on Windows.
-[target.'cfg(not(windows))'.dependencies]
+# and don't depend on this on Windows.  The same applies on s390x.
+[target.'cfg(not(any(windows, target_arch = "s390x")))'.dependencies]
 rusty_v8 = "0.27"
 
 [dev-dependencies]

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);