Remove dead musl-tools step and link hello_cpp from Rust

The musl-tools install step can never run now that all musl targets on
Linux use cross. Remove it to avoid confusion.

Also call hello_cpp() from bin1.rs so the C++ runtime is actually linked,
making the test cover linker failures as well as compiler failures.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: autarch

action.yml

@@ -157,18 +157,6 @@ runs:
       env:
         GITHUB_TOKEN: ${{ inputs.GITHUB_TOKEN }}
 
-    - name: Install musl-tools on Linux if target includes "musl"
-      shell: bash
-      run: |
-        if dpkg -l musl-tools | grep -q "^ii\s*musl-tools"; then
-            exit 0
-        fi
-        sudo apt-get update --yes && \
-            sudo apt-get install --yes musl-tools
-      if:
-        steps.determine-cross-compile.outputs.needs-cross != 'true' && contains(inputs.target,
-        'musl')
-
     - name: Set build command
       id: set-build-command
       shell: bash

test-project/src/bin1.rs

@@ -1,4 +1,9 @@
+extern "C" {
+    fn hello_cpp() -> i32;
+}
+
 fn main() {
+    let _ = unsafe { hello_cpp() };
     println!("Hello, world!");
 }