fix: avoid shared IPv4 miscompilation on Rust 1.95 (#2703)

Keep ipv4_inet out of line to prevent LLVM load combining from
zeroing the address and prefix when inlined into async add_ip.
This works around Windows named-NIC IPv4 setup failures on the
current release toolchain.

Link the upstream LLVM fix so the workaround can be removed once
all build toolchains include it.

Fixes #2696

easytier/src/instance/shared_virtual_nic.rs

@@ -896,6 +896,10 @@ impl SharedVirtualNicRegistry {
     }
 }
 
+// Rust 1.95's LLVM can zero this result when inlined into the async add_ip path.
+// Remove this workaround once all build toolchains include LLVM's fix:
+// https://github.com/llvm/llvm-project/pull/207229
+#[inline(never)]
 fn ipv4_inet(address: Ipv4Addr, prefix: i32) -> Result<Ipv4Inet, Error> {
     let prefix = u8::try_from(prefix)
         .map_err(|_| anyhow::anyhow!("invalid IPv4 prefix length {}", prefix))?;