add wasmtime adapter and stdio wrappers

the stdio wrappers will not work on windows, but thats a whole other can
of worms anyway

crates/wasi-c2/Cargo.toml

@@ -13,6 +13,11 @@ include = ["src/**/*", "LICENSE", "build.rs"]
 build = "build.rs"
 publish = false
 
+# This doesn't actually link to a native library, but it allows us to set env
+# vars like `DEP_WASI_C2_19_*` for crates that have build scripts and depend
+# on this crate, allowing other crates to use the same witx files.
+links = "wasi-c2-19"
+
 [dependencies]
 anyhow = "1.0"
 thiserror = "1.0"