if NO_OBJ is defined, but not about the value.
Which means you cannot unset NO_OBJ on the command line or with env variable:
$ make NO_OBJ=""
or
$ export NO_OBJ=""; make
I still think that 'make obj' doesn't really work for the doc
project. But for now, you have to disable it yourself on the command
line or in your ~/.profile.
This is a revert of r51065