The old uses `abspath`, which I think is so harmful:
* If I `cp -a` the whole project, `build/tools/caffe` still refer to
the old file, until `make clean`, making debugging very hard
* For `tar` and `scp`, the soft links can not work
unless the target project folder has the same path
# Target for extension-less symlinks to tool binaries with extension '*.bin'.
$(TOOL_BUILD_DIR)/%: $(TOOL_BUILD_DIR)/%.bin | $(TOOL_BUILD_DIR)
@ $(RM) $@
- @ ln -s $(abspath $<) $@
+ @ ln -s $(notdir $<) $@
$(TOOL_BINS): %.bin : %.o | $(DYNAMIC_NAME)
@ echo CXX/LD -o $@