libkrun: Produce a proper Rust library

Produce a proper Rust library to avoid the need for C library
installation as well as binding generation/definition. Basically, we can
now reference the crate via Cargo.toml:

  [dependencies]
  libkrun = ...

instead of having to rely on constructs like:

  #[link(name = "krun")]
  extern "C" {
    pub fn krun_create_ctx() -> i32;
    ...
  }

Signed-off-by: Daniel Müller <deso@posteo.net>

Author: d-e-s-o

src/libkrun/Cargo.toml

@@ -46,4 +46,4 @@ vm-memory = { version = "0.17", features = ["backend-mmap"] }
 
 [lib]
 name = "krun"
-crate-type = ["cdylib"]
+crate-type = ["cdylib", "lib"]