Make the wasmtime-wasi-c dependency conditional on Unix.

Cargo.toml

@@ -31,7 +31,6 @@ wasmtime-jit = { path = "wasmtime-jit" }
 wasmtime-obj = { path = "wasmtime-obj" }
 wasmtime-wast = { path = "wasmtime-wast" }
 wasmtime-wasi = { path = "wasmtime-wasi" }
-wasmtime-wasi-c = { path = "wasmtime-wasi-c" }
 docopt = "1.0.1"
 serde = "1.0.75"
 serde_derive = "1.0.75"
@@ -43,6 +42,9 @@ wabt = "0.7"
 libc = "0.2.50"
 errno = "0.2.4"
 
+[target.'cfg(unix)'.dependencies]
+wasmtime-wasi-c = { path = "wasmtime-wasi-c" }
+
 [workspace]
 
 [features]

src/wasmtime.rs

@@ -50,9 +50,11 @@ use std::process::exit;
 use wabt;
 use wasmtime_jit::{ActionOutcome, Context};
 use wasmtime_wasi::instantiate_wasi;
-use wasmtime_wasi_c::instantiate_wasi_c;
 use wasmtime_wast::instantiate_spectest;
 
+#[cfg(unix)]
+use wasmtime_wasi_c::instantiate_wasi_c;
+
 static LOG_FILENAME_PREFIX: &str = "wasmtime.dbg.";
 
 const USAGE: &str = "
@@ -235,8 +237,15 @@ fn main() {
     let wasi = if args.flag_wasi_common {
         instantiate_wasi("", global_exports, &preopen_dirs, &argv, &environ)
     } else {
+        #[cfg(unix)]
+        {
             instantiate_wasi_c("", global_exports, &preopen_dirs, &argv, &environ)
         }
+        #[cfg(not(unix))]
+        {
+            unimplemented!("wasmtime-wasi-c requires a *nix")
+        }
+    }
     .expect("instantiating wasi");
 
     context.name_instance("wasi_unstable".to_owned(), wasi);