In order to have the recipe qtbase compiling it is necessary to add -lGLESv2 to the QMAKE_LIBS_EGL variable.
Right now... when I add the option gles2 we get only the -lEGL. I was more expecting something like -lGLESv2.

If we have a look to the mkspecs of the pi2, we can see:
QMAKE_LIBS_EGL = "-lEGL -lGLESv2"

It seems weird to add the library GLESv2 when we select the exact name option.

The problem might be somewhere in meta-qt5, meta-raspberrypi or qtbase.