I have the same issue. As you can see in your 'config.log', qt will use the bundled copy of harfbuzz (actually harfbuzz-ng). Yet, it seems that for some reason it doesn't compile harfbuzz-ng when one runs 'make'.
I went to qt-everywhere-opensource-src-5.4.0/qtbase/src/3rdparty/harfbuzz-ng and manually ran 'make' and harfbuzz-ng compiled. Afterwards I went back to qt-everywhere-opensource-src-5.4.0 and ran 'make' again. It got past the errors with 'harfbuzz', but my build now fails with the error:
Makefile:57: recipe for target 'sub-src-install_subtargets' failed
make[1]: *** [sub-src-install_subtargets] Error 2