ci : fix macos x86 build (ggml-org#7940)

In order to use old `macos-latest` we should use `macos-12`

Potentially will fix: ggml-org#6975

Author: olexiyb

.github/workflows/build.yml

@@ -84,7 +84,7 @@ jobs:
           name: llama-bin-macos-arm64.zip
 
   macOS-latest-cmake-x64:
-    runs-on: macos-latest
+    runs-on: macos-12
 
     steps:
       - name: Clone