GUB failure

[Phil Holmes]

I'm getting the following failure running a GUB build:

/home/gub/NewGub/gub/target/darwin-ppc/src/lilypond-git.sv.gnu.org--
lilypond.git-release-unstable/flower/warn.cc:114:49: warning: format '%d'
expects argument of type 'int', but argument 2 has type 
'std::vector<std::basic_string<char> >::size_type {aka long unsigned int}' 
[-Wformat=]
                        expected_warnings.size ());
                                                 ^

Presumably caused by

Issue 4550 (n/2) Avoid "using namespace std;" in included files

but I've no idea why.  Can anyone suggest a fix, please?