See attached build log. (Please do not complain about the need for looking at the build log until you can provide an easy way to open bugs with the correct data picked out of a tinderbox log. Thanks.)
Created attachment 252879 [details] Build log
After a sed hack on the LINKFLAGS, you got your LDFLAGS passed to the shared library, with CXXFLAGS as a bonus: x86_64-pc-linux-gnu-g++ -o src/libmapnik.so -Wl,-rpath-link,. -Wl,-soname,libmapnik.so.0.7 -Wl,-O1 -Wl,--as-needed -shared src/agg_renderer.os src/datasource_cache.os src/color.os src/envelope.os src/filter_factory.os src/font_engine_freetype.os src/font_set.os src/graphics.os src/image_reader.os src/image_util.os src/layer.os src/line_pattern_symbolizer.os src/map.os src/load_map.os src/memory.os src/params.os src/placement_finder.os src/plugin.os src/png_reader.os src/point_symbolizer.os src/polygon_pattern_symbolizer.os src/save_map.os src/shield_symbolizer.os src/text_symbolizer.os src/tiff_reader.os src/wkb.os src/projection.os src/proj_transform.os src/distance.os src/scale_denominator.os src/memory_datasource.os src/stroke.os src/symbolizer.os src/arrow.os src/unicode.os src/cairo_renderer.os src/libxml2_loader.os -Lsrc -L/usr/lib64 -L/usr/lib64/boost-1_42 -L/usr/lib64/postgresql-9.0/lib64 -lfreetype -lltdl -lpng -ltiff -lz -ljpeg -lproj -licuuc -lagg -lboost_filesystem -lboost_regex -lcairomm-1.0 -lcairo -lxml2 -lboost_thread -lagg
