Use bindgen as a program rather than as a library

This allows us to remove the `kernel` `build.rs` script
and simplifies the build. `Cargo.lock` is tiny now.
The shlex dependency also goes away.

Note that this commit does *not* use the list of included
functions/types/vars etc., so it is not equivalent.

Signed-off-by: Finn Behrens <me@kloenk.de>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: kloenk

.github/workflows/ci.yaml

@@ -16,6 +16,7 @@ jobs:
       - run: sudo apt update
       - run: sudo apt install libelf-dev qemu-system-x86 busybox-static
       - run: rustup default nightly-2020-08-27
+      - run: rustup component add rustfmt
       - run: rustup component add rust-src
 
       # Build

Cargo.lock

@@ -3,7 +3,6 @@
 # TODO: generate automatically
 [workspace]
 members = [
-    "rust/shlex",
     "rust/module",
     "rust/kernel",
     "drivers/char/rust_example",