Fix Bazel tool resolution for bubblewrap and voice builds (#61254)

## What changed

- Use the Bazel coreutils toolchain's `sha256sum` to generate `CODEX_BWRAP_SHA256` for bubblewrap.
- Add the running Python interpreter's directory to `PATH` for Unix native voice builds so GLib generators using `env python3` can find it.

## Testing

Add a regression test verifying that a Unix generator using `env python3` runs with the recipe's interpreter.

GitOrigin-RevId: 52694cc09c92db27bc117217d3833a35524ff304

third_party/voice/build_native.py

@@ -135,14 +135,12 @@ class NativeBuild:
         }
         if windows_inputs is not None:
             self.environment.pop("LIBPATH", None)
-        paths = [
-            str(self.tools / "bin"),
-            *(
-                []
-                if windows_inputs is not None
-                else [str(p.parent) for p in self.toolchain.values()]
-            ),
-        ]
+        paths = [str(self.tools / "bin")]
+        if not self.windows:
+            # GLib generators use /usr/bin/env python3 even when Meson runs under Bazel.
+            paths.append(str(Path(sys.executable).parent))
+        if windows_inputs is None:
+            paths.extend(str(p.parent) for p in self.toolchain.values())
         paths += (
             inherited_environment.get("PATH", "").split(os.pathsep)
             if self.windows

third_party/voice/test_build_native.py

@@ -85,6 +85,21 @@ class NativeBuildTests(unittest.TestCase):
             NativeBuild(self.args, self.environment)
         self.assertFalse(self.args.output.exists())
 
+    @unittest.skipIf(os.name == "nt", "Exercises a Unix generator shebang")
+    def test_generator_uses_the_recipe_interpreter(self):
+        python = self.root / "runtime" / "bin" / "python3"
+        python.parent.mkdir(parents=True)
+        python.symlink_to(sys.executable)
+        with patch("sys.executable", str(python)):
+            build = NativeBuild(self.args, self.environment)
+        generator = self.root / "generator"
+        generator.write_text(
+            "#!/usr/bin/env python3\nimport sys\nprint(sys.executable)\n"
+        )
+        generator.chmod(0o755)
+        result = subprocess.check_output([generator], env=build.environment, text=True)
+        self.assertEqual(result.strip(), str(python))
+
     @unittest.skipIf(os.name == "nt", "Exercises the Unix clang++ driver symlink")
     def test_bootstrap_links_cpp_runtime_through_compiler_symlink(self):
         tools = {name: shutil.which(name) for name in ("clang", "cmake", "make")}