feat: add write_stamp function and update development environment with libmpc

docs/development-environment.md

@@ -11,8 +11,8 @@ remote-bitbang debug acceptance flow. Docker, Nix, and manual Ubuntu installs
 provide Java 17 for SBT. Docker and Nix use Python 3.10 to match the
 hash-pinned Ubuntu 22.04 requirement sets. The environment also installs the
 locked Python build and quality dependencies, clang-format-14, GNU Make,
-C/C++ build tools, Perl for Verilator, and runtime libraries required by those
+C/C++ build tools, Perl for Verilator, GNU MPC for the RISC-V compiler, and
-binaries.
+runtime libraries required by those binaries.
 
 The environment intentionally does not include PDK repositories, managed RTL,
 application archives, build output, or compiler caches. These inputs are
@@ -37,6 +37,8 @@ dependency lock, selected tool set, or Python requirement hashes change.
 Installed public tool archives are made readable and their directories
 traversable by all users. This is required when Docker builds the image as root
 and runs regressions with the caller's user ID.
+The environment stamp and activation script are also world-readable so those
+runtime users can verify and activate the root-built environment.
 
 ~~~sh
 python3 scripts/development_environment.py bootstrap

flake.nix

@@ -61,6 +61,7 @@
           gperftools
           launcher
           libunwind
+          libmpc
           mold
           ncurses5
           numactl

scripts/development_environment.py

@@ -166,6 +166,11 @@ def write_activation(path: Path, content: str) -> None:
     path.chmod(0o644)
 
 
+def write_stamp(path: Path, content: dict[str, Any]) -> None:
+    atomic_write(path, json.dumps(content, indent=2, sort_keys=True) + "\n")
+    path.chmod(0o644)
+
+
 def run(command: list[str]) -> None:
     print("+ " + " ".join(shlex.quote(argument) for argument in command), flush=True)
     subprocess.run(command, check=True)
@@ -205,7 +210,7 @@ def bootstrap(args: argparse.Namespace) -> int:
         for name in tools:
             install(name, available[name], cache, update=args.update)
         create_virtualenv(root, cache)
-        atomic_write(cache / STAMP_NAME, json.dumps(expected_stamp, indent=2, sort_keys=True) + "\n")
+        write_stamp(cache / STAMP_NAME, expected_stamp)
     activation = args.output.resolve() if args.output else cache / ACTIVATE_NAME
     write_activation(
         activation,

tests/test_script_tools.py

@@ -38,6 +38,7 @@ from scripts.development_environment import (  # noqa: E402
     render_activation,
     stamp_data,
     write_activation,
+    write_stamp,
 )
 from scripts.generate_mpw import render_active_manifest, validate_extension_bindings  # noqa: E402
 from scripts.install_toolchain import make_tree_world_readable, safe_extract  # noqa: E402
@@ -1183,6 +1184,10 @@ def test_development_environment_contract_is_lock_pinned(tmp_path: Path) -> None
     activation_path = tmp_path / "activate.sh"
     write_activation(activation_path, activation)
     assert activation_path.stat().st_mode & 0o777 == 0o644
+    stamp_path = tmp_path / "development-environment.json"
+    write_stamp(stamp_path, stamp)
+    assert json.loads(stamp_path.read_text(encoding="utf-8")) == stamp
+    assert stamp_path.stat().st_mode & 0o777 == 0o644
 
 
 def test_container_and_nix_environment_files_use_locked_inputs() -> None:
@@ -1198,6 +1203,7 @@ def test_container_and_nix_environment_files_use_locked_inputs() -> None:
     assert "scripts/development_environment.py" in flake
     assert "buildFHSEnv" in flake
     assert "jdk17_headless" in flake
+    assert "          libmpc\n" in flake
     assert "          perl\n" in flake
     assert "python310Full" in flake
     assert "python3Full" not in flake