add a new export func showing use of output-stream, whose implementations are defined in host and wasi-common. this one works because we are using host::wasi::streams::add_to_linker(...).
add a new export func showing passing filesystem's descriptor-stat. by using bindgen's with syntax, we get to use the definition of this struct & its children from host::wasi, rather than a locally created definition.
hostandwasi-common. this one works because we are usinghost::wasi::streams::add_to_linker(...).withsyntax, we get to use the definition of this struct & its children fromhost::wasi, rather than a locally created definition.