[wiggle] Don't make generated structs and unions Copy.

Some structs and unions are large enough that making them `Copy` isn't
ideal. wasi-common only needed `Copy` in a few places that were easy to
fix. `SubscriptionClock` is 32 bytes, so it's not a bad a idea to pass
it by reference anyway.

crates/wasi-common/src/clock.rs

@@ -5,7 +5,7 @@ use std::time::SystemTime;
 
 pub(crate) use sys::clock::*;
 
-pub(crate) fn to_relative_ns_delay(clock: SubscriptionClock) -> Result<u128> {
+pub(crate) fn to_relative_ns_delay(clock: &SubscriptionClock) -> Result<u128> {
     if clock.flags != Subclockflags::SUBSCRIPTION_CLOCK_ABSTIME {
         return Ok(u128::from(clock.timeout));
     }

crates/wasi-common/src/snapshots/wasi_snapshot_preview1.rs

@@ -1185,7 +1185,7 @@ impl<'a> WasiSnapshotPreview1 for WasiCtx {
         for subscription in subscriptions {
             match subscription.u {
                 types::SubscriptionU::Clock(clock) => {
-                    let delay = clock::to_relative_ns_delay(clock)?;
+                    let delay = clock::to_relative_ns_delay(&clock)?;
                     log::debug!("poll_oneoff event.u.clock = {:?}", clock);
                     log::debug!("poll_oneoff delay = {:?}ns", delay);
                     let current = poll::ClockEventData {

crates/wasi-common/src/wasi.rs

@@ -95,7 +95,7 @@ impl AsBytes for types::Dirent {
         let mut bytes: Vec<u8> = Vec::with_capacity(offset);
         bytes.resize(offset, 0);
         let ptr = bytes.as_mut_ptr() as *mut Self;
-        unsafe { ptr.write_unaligned(*self) };
+        unsafe { ptr.write_unaligned(self.clone()) };
         Ok(bytes)
     }
 }

crates/wiggle/crates/generate/src/types/struct.rs

@@ -74,7 +74,7 @@ pub(super) fn define_struct(
     let (struct_lifetime, extra_derive) = if s.needs_lifetime() {
         (quote!(<'a>), quote!())
     } else {
-        (quote!(), quote!(, Copy, PartialEq))
+        (quote!(), quote!(, PartialEq))
     };
 
     let transparent = if s.is_transparent() {

crates/wiggle/crates/generate/src/types/union.rs

@@ -68,7 +68,7 @@ pub(super) fn define_union(names: &Names, name: &witx::Id, u: &witx::UnionDataty
     let (enum_lifetime, extra_derive) = if u.needs_lifetime() {
         (quote!(<'a>), quote!())
     } else {
-        (quote!(), quote!(, Copy, PartialEq))
+        (quote!(), quote!(, PartialEq))
     };
 
     quote! {