feat(vecadd): add llvm19 feature passthrough to cuda_builder

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: brandonros

container/ubuntu24-cuda13-llvm19/Dockerfile

@@ -1,4 +1,4 @@
-FROM nvcr.io/nvidia/cuda:13.0.2-cudnn-devel-ubuntu24.04 AS llvm-builder
+FROM nvcr.io/nvidia/cuda:13.2.1-cudnn-devel-ubuntu24.04 AS llvm-builder
 
 RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get -qq -y install \
     build-essential \
@@ -51,7 +51,7 @@ RUN curl -sSf -L -O https://github.com/llvm/llvm-project/releases/download/llvmo
     cd ../.. && \
     rm -rf llvm-project-19.1.7.src*
 
-FROM nvcr.io/nvidia/cuda:13.0.2-cudnn-devel-ubuntu24.04
+FROM nvcr.io/nvidia/cuda:13.2.1-cudnn-devel-ubuntu24.04
 
 RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get -qq -y install \
     build-essential \

examples/vecadd/Cargo.toml

@@ -3,6 +3,13 @@ name = "vecadd"
 version = "0.1.0"
 edition = "2024"
 
+[features]
+default = []
+# Build the kernels crate with the LLVM 19 backend. Forwards to `cuda_builder`,
+# which propagates the feature to `nvvm` (default arch -> Compute100 / Blackwell)
+# and to its nested `cargo build -p rustc_codegen_nvvm`.
+llvm19 = ["cuda_builder/llvm19"]
+
 [dependencies]
 cust = { path = "../../crates/cust" }
 cust_raw = { path = "../../crates/cust_raw", default-features = false, features = ["driver"] }