Set KDE_INSTALL_BINDIR to avoid:
KDE_INSTALL_BINDIR, KDE_INSTALL_LIBDIR and KDE_INSTALL_INCLUDEDIR should
either all be absolute paths or all be relative paths.

Set -Wno-dev to avoid:
"hi128-apps-kid3.png" has characters before the size; it should be renamed
to "128-apps-kid3.png"

This cannot be fixed without breaking compatibility with KDE 4.

The "ID header_left already defined" warnings cannot be fixed, they
seem to be a bug in libxml2-2.9.2, see
https://bugzilla.gnome.org/show_bug.cgi?id=737840