call __wasm_call_ctors in all exported functions

Now that we've updated to the latest Rust Spin SDK, which uses a newer
`wit-bindgen`, we need to call `__wasm_call_ctors` explicitly in order to
initialize `wasi-libc` (e.g. grab environment variables, etc.).  Previously,
this was done implicitly, but that caused other problems, so `wit-bindgen` does
it explicitly, which has the side effect of telling `wasm-ld` _not_ to do it
implicitly.

Signed-off-by: Joel Dice <[email protected]>

Author: dicej

.gitignore

@@ -1,5 +1,4 @@
 /target
-/Cargo.lock
 __pycache__
 *.wasm
-.spin
+.spin