python-egg-info is broken in 1.2

[HanabishiRecca]

I don't know how noone noticed it, but this part is broken:

libtorrent/bindings/python/CMakeLists.txt

Lines 116 to 121 in fda40ea

	add_custom_command(OUTPUT ${OUTPUT}
	COMMAND ${Python3_EXECUTABLE} ${SETUP_PY} build -b "${CMAKE_CURRENT_SOURCE_DIR}"
	COMMAND ${Python3_EXECUTABLE} ${SETUP_PY} egg_info -b "${CMAKE_CURRENT_SOURCE_DIR}"
	COMMAND ${CMAKE_COMMAND} -E touch ${OUTPUT}
	DEPENDS ${DEPS}
	)

It is fixed in 2.0 via 932ddd3 and 509d7e1. So the change simply should be backported to 1.2.