Remove the shim kernel crate

kernel/src/syscall/getppid.rs

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use super::SyscallReturn;
+use crate::prelude::*;
+
+pub fn sys_getppid(ctx: &Context) -> Result<SyscallReturn> {
+    let parent = ctx.process.parent();
+    match parent {
+        None => Ok(SyscallReturn::Return(0)),
+        Some(parent) => Ok(SyscallReturn::Return(parent.pid() as _)),
+    }
+}