Enable env_logger in the C API

This commit ensures that `env_logger` and `RUST_LOG` are configured to
work with the C API.

Author: alexcrichton

Cargo.lock

@@ -17,6 +17,7 @@ test = false
 doctest = false
 
 [dependencies]
+env_logger = "0.7"
 anyhow = "1.0"
 once_cell = "1.3"
 wasmtime = { path = "../wasmtime", default-features = false }

crates/c-api/Cargo.toml

@@ -11,6 +11,7 @@ wasmtime_c_api_macros::declare_own!(wasm_engine_t);
 
 #[no_mangle]
 pub extern "C" fn wasm_engine_new() -> Box<wasm_engine_t> {
+    drop(env_logger::try_init());
     Box::new(wasm_engine_t {
         engine: HostRef::new(Engine::default()),
     })