Remove the shim kernel crate

kernel/src/syscall/msync.rs

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use super::SyscallReturn;
+use crate::prelude::*;
+
+pub fn sys_msync(_start: Vaddr, _size: usize, _flag: i32, _ctx: &Context) -> Result<SyscallReturn> {
+    // TODO: implement real `msync`.
+    Ok(SyscallReturn::Return(0))
+}