what is LLVMOBJDIR?

In http://llvm.org/svn/llvm-project/llvm-gcc-4-2/trunk/README.LLVM I can
read "Below we assume the LLVM OBJDIR is $LLVMOBJDIR".

But in http://llvm.org/docs/GettingStarted.html#terminology I read about
OBJ_ROOT. Is this the same? Then terminology is inconsistent. But
actually I don't think so, because the text says "These are not
environment variables". Still it's confusing, because I was asked to
set some objdir to an environment, haven't I ?? (see previous
paragraph)

Moreover, the Makefile.config from SVN trunk doesn't know an "LLVM
OBJDIR". It knows LLVM_OBJ_ROOT and PROG_OBJ_ROOT. So where is
this "LLVM OBJDIR" ?!?!

All I all, I now don't know if I have to issue the command "export
LLVMOBJDIR=xyz" command --- or not. And If I have to do this, I don't
have the slightest clue as to what xyz might be.

BTW, I compiled llvm from SVN trunk with:

$ ./configure \
        --prefix=/usr/src/llvm/dist \
        --enable-optimized \
        --enable-assertions

$ make ENABLE_OPTIMIZED=1
$ make install

that worked without a flaw.