Add cpp back

.github/workflows/main.yml

@@ -86,7 +86,7 @@ jobs:
 
     # Install build dependencies
     - name: Install dependencies
-      run: sudo apt-get update && sudo apt-get install -y cpio rsync bc makeself gcc
+      run: sudo apt-get update && sudo apt-get install -y cpio rsync bc makeself gcc cpp
 
     # Restore build and download caches. We key these based on timestamps and build
     # target, since these essentially "accumulate" useful information (such as source