strigi @0.7.8: build fails on 10.6.8: error: no matching function for call to 'make_pair'

[kencu (Ken)]

cd /opt/local/var/macports/build/_opt_macports-ports_devel_strigi/strigi/work/build/strigiutils/bin/xmlindexer && /opt/local/bin/clang++-mp-9.0   -I/opt/local/var/macports/build/_opt_macports-ports_devel_strigi/strigi/work/strigi-0.7.8/libstreams/include -I/opt/local/var/macports/build/_opt_macports-ports_devel_strigi/strigi/work/build/libstreams/include -I/opt/local/var/macports/build/_opt_macports-ports_devel_strigi/strigi/work/strigi-0.7.8/libstreamanalyzer/include -I/opt/local/var/macports/build/_opt_macports-ports_devel_strigi/strigi/work/build/libstreamanalyzer/include  -pipe -Os -DU_NOEXCEPT= -stdlib=libc++ -DNDEBUG -arch x86_64 -mmacosx-version-min=10.6   -o CMakeFiles/libxmlindexer.dir/xmlindexer.cpp.o -c /opt/local/var/macports/build/_opt_macports-ports_devel_strigi/strigi/work/strigi-0.7.8/strigiutils/bin/xmlindexer/xmlindexer.cpp
/opt/local/var/macports/build/_opt_macports-ports_devel_strigi/strigi/work/strigi-0.7.8/libstreamanalyzer/plugins/indexers/clucenengindexer/cluceneindexreader.cpp:324:31: error: no matching function for call to 'make_pair'
        doc.properties.insert(make_pair<const string, string>(
                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/local/libexec/llvm-9.0/bin/../include/c++/v1/utility:667:1: note: candidate function template not viable: no known conversion from 'std::__1::string' (aka 'basic_string<char, char_traits<char>, allocator<char> >') to 'std::__1::basic_string<char> &&' for 2nd argument
make_pair(_T1&& __t1, _T2&& __t2)
^
[ 82%] Linking CXX static library liblibdeepgrep.a

forcing the build with clang-5.0 succeeds, however.