Honor build-script execution constraints in compilation and run actions

cargo/private/cargo_build_script_wrapper.bzl

@@ -200,6 +200,7 @@ def cargo_build_script(
     # it is translated to `target_compatible_with` to match the `cfg = "exec"`
     # consumption of the target.
     script_kwargs["target_compatible_with"] = exec_compatible_with
+    script_kwargs["exec_compatible_with"] = exec_compatible_with
 
     binary_tags = depset(
         (tags if tags else []) + ["manual"],
@@ -241,6 +242,7 @@ def cargo_build_script(
     # This target executes the build script.
     _build_script_run(
         name = name,
+        exec_compatible_with = exec_compatible_with,
         script = ":{}_".format(name),
         data_runfiles = ":{}-".format(name),
         data = data,

cargo/tests/cargo_build_script/compatible_with/BUILD.bazel

@@ -1,5 +1,6 @@
 load("//cargo:defs.bzl", "cargo_build_script")
 load("//rust:defs.bzl", "rust_library", "rust_test")
+load(":exec_constraints_test.bzl", "exec_constraints_test")
 
 environment_group(
     name = "foo_environment",
@@ -39,3 +40,18 @@ rust_test(
     edition = "2018",
     deps = [":empty_build_script"],
 )
+
+cargo_build_script(
+    name = "exec_constrained_build_script",
+    testonly = True,
+    srcs = ["do_nothing.rs"],
+    edition = "2018",
+    exec_compatible_with = ["@platforms//os:linux"],
+    tags = ["manual"],
+)
+
+exec_constraints_test(
+    name = "exec_constraints_test",
+    build_script = "exec_constrained_build_script",
+    constraint = "@platforms//os:linux",
+)

cargo/tests/cargo_build_script/compatible_with/exec_constraints_test.bzl

@@ -0,0 +1,20 @@
+"""Check that a Cargo build script constrains both execution stages."""
+
+def exec_constraints_test(name, build_script, constraint):
+    """Assert macro expansion forwards the execution constraint to both actions.
+
+    Args:
+        name: Name of the generated test suite.
+        build_script: Build script target to inspect.
+        constraint: Expected execution constraint label.
+    """
+    expected = str(Label(constraint))
+    for target in [build_script + "_", build_script]:
+        rule = native.existing_rule(target)
+        if rule == None:
+            fail("missing build script target " + target)
+        actual = rule.get("exec_compatible_with", [])
+        if len(actual) != 1 or str(actual[0]) != expected:
+            fail("{} must execute on {}, got {}".format(target, expected, actual))
+
+    native.test_suite(name = name, tests = [":test_compatible_with"])