Remove the shim kernel crate

kernel/src/syscall/getgid.rs

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use super::SyscallReturn;
+use crate::prelude::*;
+
+pub fn sys_getgid(ctx: &Context) -> Result<SyscallReturn> {
+    let gid = ctx.posix_thread.credentials().rgid();
+
+    Ok(SyscallReturn::Return(gid.as_u32() as _))
+}