CI: Add z3 package to macOS as a test dependency of c2rust-refactor

Author: ahomescu

.github/workflows/ci.yml

@@ -95,7 +95,7 @@ jobs:
         if: runner.os == 'macOS'
         run: |
           # `bash` needed b/c macOS ships with bash 3, which doesn't support arrays properly
-          brew install -q cmake ninja gpg llvm@${{ matrix.clang-version }} bash
+          brew install -q cmake ninja gpg llvm@${{ matrix.clang-version }} bash z3
 
       - name: cargo build --release
         run: |