tools: Use ClangDriver in divcc.

tools/divcc.cpp

@@ -330,8 +330,7 @@ int main( int argc, char **argv )
         {
             if ( po.hasVersion )
                 std::cout << "divine version: " << ui::version() << "\n";
-            cc::Diagnostics diag;
-            driver::Driver drv( "/usr/bin/false", LLVM_HOST_TRIPLE, diag.engine );
+            cc::ClangDriver drv;
             drv.BuildCompilation( { "divcc", po.hasHelp? "--help" : "--version" } );
             return 0;
         }