tools: generate_syscall_library script

very initial version of a tool that generates libraries from syn-serde
dumps of tock capsules

```
❯ ./generate_syscall_library.py ../button.json

extern "C" {

returncode_t libtock_button_command_enable_interrupt();

returncode_t libtock_button_command_disable_interrupt();

returncode_t libtock_button_command_read();

}
```

tools/generate_syscall_library.py

@@ -0,0 +1,127 @@
+#!/usr/bin/env python3
+
+# Licensed under the Apache License, Version 2.0 or the MIT License.
+# SPDX-License-Identifier: Apache-2.0 OR MIT
+# Copyright Tock Contributors 2024.
+
+"""
+git clone [email protected]:taiki-e/syn-serde.git
+cd syn-serde/examples/rust2json
+cargo run -- ../../tock/capsules/core/src/button.rs > ../../tock/button.json
+
+then run this
+
+./generate_syscall_library.py ../button.json
+"""
+
+
+import json
+import sys
+import pathlib
+from pathlib import Path
+
+sys.setrecursionlimit(10**6)
+
+syntax_filename = sys.argv[1]
+capsule = pathlib.Path(syntax_filename).stem
+
+
+def search(tree, goal):
+    if isinstance(tree, list):
+        found = []
+        for i in tree:
+            r = search(i, goal)
+            if r != None:
+                found.extend(r)
+        return found
+
+    elif isinstance(tree, dict):
+        found = []
+        for k, v in tree.items():
+            if k == goal:
+                found.append(v)
+                continue
+            r = search(v, goal)
+            if r != None:
+                found.extend(r)
+        return found
+    else:
+        if goal == tree:
+            return [tree]
+        return None
+
+    return None
+
+
+def find_matching_fn(fns, search_fn):
+    for fn in fns:
+        function_name = fn["ident"]
+        if function_name == search_fn:
+            return fn
+
+
+commands = []
+fns = None
+
+
+with open(syntax_filename) as f:
+    s = json.load(f)
+
+    fns = search(s, "fn")
+
+    fn = find_matching_fn(fns, "command")
+
+    function_name = fn["ident"]
+
+    if function_name == "command":
+        fn_body = fn["stmts"]
+
+        match_stmt = search(fn_body, "match")[0]
+
+        match_arms = match_stmt["arms"]
+
+        for arm in match_arms:
+            try:
+                command_index = arm["pat"]["lit"]["int"]
+
+                if command_index == 0:
+                    continue
+
+                op = arm["body"]["method_call"]["method"]
+
+                commands.append((command_index, op))
+            except:
+                pass
+
+c_header = """
+#pragma once
+
+#include "../../tock.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+"""
+print(c_header)
+
+c_fn_format = """
+{comment}
+returncode_t libtock_{capsule}_{fn_name}();
+"""
+
+for commandnum, fn_name in commands:
+    fn = find_matching_fn(fns, fn_name)
+
+    c_fn = c_fn_format.format(comment="", capsule=capsule, fn_name=fn_name)
+
+    print(c_fn)
+
+c_footer = """
+
+#ifdef __cplusplus
+}
+#endif
+"""
+
+print(c_footer)