Add BUILD file for proc-macro2 kleaf build

Test:
touch external/rust/crates/unicode-ident/WORKSPACE && \
touch external/rust/crates/proc-macro2/WORKSPACE && \
b build @proc-macro2 \
  --override_repository=unicode-ident=external/rust/crates/unicode-ident/ \
  --override_repository=proc-macro2=external/rust/crates/proc-macro2/
Bug: 304282799

Change-Id: If577c7b605f4415c95eabeafe007134c5d45671b

1 files changed, 59 insertions, 0 deletions

diff --git a/BUILD b/BUILD
new file mode 100644
index 0000000..7d96008
--- /dev/null
+++ b/BUILD
@@ -0,0 +1,59 @@
+load("@rules_license//rules:license.bzl", "license")
+load("@rules_license//rules:license_kind.bzl", "license_kind")
+load("@rules_rust//cargo:defs.bzl", "cargo_build_script")
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+package(
+    default_applicable_licenses = [":license"],
+    default_visibility = ["//visibility:public"],
+)
+
+license(
+    name = "license",
+    license_kinds = [
+        ":SPDX-license-identifier-Apache-2.0",
+        ":SPDX-license-identifier-MIT",
+    ],
+    license_text = "LICENSE-APACHE",
+    visibility = [":__subpackages__"],
+)
+
+license_kind(
+    name = "SPDX-license-identifier-Apache-2.0",
+    conditions = ["notice"],
+    url = "https://spdx.org/licenses/Apache-2.0.html",
+)
+
+license_kind(
+    name = "SPDX-license-identifier-MIT",
+    conditions = ["notice"],
+    url = "",
+)
+
+CRATE_FEATURES = [
+    "default",
+    "proc-macro",
+    "span-locations",
+]
+
+rust_library(
+    name = "proc-macro2",
+    srcs = glob(["**/*.rs"]),
+    crate_features = CRATE_FEATURES,
+    edition = "2021",
+    deps = [
+        ":proc-macro2_build_script",
+        # This should map to repo checked out from Android third party project
+        # "platform/external/rust/crates/unicode-ident".
+        "@unicode-ident",
+    ],
+)
+
+cargo_build_script(
+    name = "proc-macro2_build_script",
+    srcs = glob(["**/*.rs"]),
+    crate_features = CRATE_FEATURES,
+    crate_root = "build.rs",
+    edition = "2021",
+    visibility = ["//visibility:private"],
+)