ci: split docs job to skip llvm19-feature crates with --all-features

`--all-features` on the docs job activates `cuda_builder/llvm19`, which now
propagates `rustc_codegen_nvvm/llvm19` (added in ebfe81b for feature-graph
consistency). That forces the dep build of `rustc_codegen_nvvm` onto the LLVM
19 path, which fails in CI because no LLVM 19 toolchain is installed.

Run docs in two passes: `--all-features` over the workspace minus the three
crates that gate behind `llvm19`, then default-features over those three.
This restores green CI on the LLVM 7 path the existing images support.

Known gap: `cfg(feature = "llvm19")` code paths inside those three crates
aren't rustdoc-checked. Closing that gap properly needs LLVM 19 in the CI
images and is left as a follow-up.

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

Author: 2 people

.github/workflows/ci_linux.yml

@@ -152,14 +152,19 @@ jobs:
               --exclude cust
           '
 
-      # Exclude rustc_codegen_nvvm: `--all-features` enables its `llvm19` feature,
-      # whose build.rs requires an LLVM 19 toolchain not present in the CI image.
+      # The `llvm19` feature on `nvvm` / `cuda_builder` / `rustc_codegen_nvvm` requires
+      # an LLVM 19 toolchain that isn't in the CI image, so we can't run a single
+      # `--all-features` pass over the whole workspace. Doc those three crates with
+      # default features (the LLVM 7 path the CI image already supports) and the rest
+      # of the workspace with `--all-features`.
       - name: Check documentation
         run: |
           docker exec "$CONTAINER_NAME" bash -lc 'set -euo pipefail
             export RUSTDOCFLAGS=-Dwarnings
             cargo doc --workspace --all-features --document-private-items --no-deps \
-              --exclude rustc_codegen_nvvm
+              --exclude rustc_codegen_nvvm --exclude cuda_builder --exclude nvvm
+            cargo doc -p rustc_codegen_nvvm -p cuda_builder -p nvvm \
+              --document-private-items --no-deps
           '
 
       - name: Stop build container

.github/workflows/ci_windows.yml

@@ -123,14 +123,20 @@ jobs:
             --exclude blastoff --exclude cudnn --exclude cudnn-sys --exclude cust
 
       # Exclude crates that require cuDNN, not available on Windows CI: cudnn, cudnn-sys.
-      # Exclude rustc_codegen_nvvm: `--all-features` enables its `llvm19` feature,
-      # whose build.rs requires an LLVM 19 toolchain not present in the CI image.
+      # The `llvm19` feature on `nvvm` / `cuda_builder` / `rustc_codegen_nvvm` requires
+      # an LLVM 19 toolchain that isn't in the CI image, so we can't run a single
+      # `--all-features` pass over the whole workspace. Doc those three crates with
+      # default features (the LLVM 7 path the CI image already supports) and the rest
+      # of the workspace with `--all-features`.
       - name: Check documentation
         env:
           RUSTDOCFLAGS: -Dwarnings
         run: |
           cargo doc --workspace --all-features --document-private-items --no-deps `
-            --exclude cudnn --exclude cudnn-sys --exclude rustc_codegen_nvvm
+            --exclude cudnn --exclude cudnn-sys `
+            --exclude rustc_codegen_nvvm --exclude cuda_builder --exclude nvvm
+          cargo doc -p rustc_codegen_nvvm -p cuda_builder -p nvvm `
+            --document-private-items --no-deps
 
       # Disabled due to dll issues, someone with Windows knowledge needed
       # - name: Compiletest