rust: bssl-macros: Do not depend on std


This is a macros-only crate, obviously we do not need `libstd`.

Signed-off-by: Xiangfei Ding <xfding@google.com>
Change-Id: I80ba7537b79f5fccc799062b1c14bc176a6a6964
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/95307
Reviewed-by: David Benjamin <davidben@google.com>
Presubmit-BoringSSL-Verified: boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com <boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Adam Langley <agl@google.com>

rust/bssl-macros/src/lib.rs

diff --git a/rust/bssl-macros/src/lib.rs b/rust/bssl-macros/src/lib.rs
index 905f6a7..fca76ba 100644
--- a/rust/bssl-macros/src/lib.rs
+++ b/rust/bssl-macros/src/lib.rs
@@ -12,6 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+
+#![no_std]
+
 #[doc(hidden)]
 #[macro_export]
 macro_rules! bssl_enum {