Makefile:113: *** missing separator. Stop.

[jcb]

Hi all,
I just checked out littler from the svn repo (r178) since I want to
rebuild it against R-2-12-branch (not pleased with Rscript).
When running ./bootstrap (Ubuntu 10.4 x86_64, autoconf2.13) get the
following error:

(...)
config.status: executing depfiles commands
Makefile:113: *** missing separator. Stop

Going to the concerned line of the file Makefile I see:

AM_CFLAGS = WARNING: ignoring environment value of R_HOME
-I/usr/share/R/include

I've tried:
export R_HOME=/opt/R-2-12-branch/ ; ./bootstrap
export R_HOME=/opt/R-2-12-branch/lib64/R/ ; ./bootstrap
to no avail.

Being no expert in autoconf tools I had to ask.
Any hints on how to fix it?
Thanks in advance.
jcb!