ci: Add LLVM to PATH on macOS

Our new build.rs in bpf-linker expects `llvm-config` to be present in
`PATH` in order to find the prefix with LLVM libraries.

.github/workflows/ci.yml

@@ -82,8 +82,11 @@ jobs:
         with:
           tool: cargo-generate
 
-      - run: brew update && brew install filosottile/musl-cross/musl-cross llvm
-        if: runner.os == 'macos'
+      - if: runner.os == 'macos'
+        run: |
+          set -euxo pipefail
+          brew update && brew install filosottile/musl-cross/musl-cross llvm
+          echo $(brew --prefix llvm)/bin >> $GITHUB_PATH
 
       - run: cargo install bpf-linker --git https://github.com/aya-rs/bpf-linker.git --no-default-features --features llvm-21
         if: runner.os == 'macos'