Actually apply CBMC patch (#3436)

The patch introduced in #3431 not only needs to be created, but also
needs to be applied.

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 and MIT licenses.

scripts/setup/al2/install_cbmc.sh

@@ -93,6 +93,7 @@ cat > varargs.patch << "EOF"
    }
 
 EOF
+patch -p1 < varargs.patch
 
 cmake3 -S . -Bbuild -DWITH_JBMC=OFF -Dsat_impl="minisat2;cadical" \
   -DCMAKE_C_COMPILER=gcc10-cc -DCMAKE_CXX_COMPILER=gcc10-c++ \