Workarounds for "automake does not support info_TEXINFOS being defined conditionally"

[Brooks Moses]

Hello!

I'm working on a bit of the binutils source tree with an automake setup, 
and I'd like to add a configure-time option to enable or disable the 
building of a particular bit of documentation.  I first tried out the 
naive way, of using AM_CONDITIONAL and this bit in Makefile.am:

-----------------------------------------------
if INTERNAL_DOCS
  info_TEXINFOS = bfd.texinfo
endif
-----------------------------------------------

This resulted in the error quoted in the subject line, "automake does 
not support info_TEXINFOS being defined conditionally", followed by an 
Internal Error.  (Incidentally, would it be possible to have automake 
just quit after the first error?  I nearly missed it hiding before all 
the noise of the Internal Error!)

I should note that I'm using automake 1.9.6, which seems to be the 
standard for the binutils tree.

Is there a workaround or other solution to do what I want?  I tried 
defining an INFOFILES variable in the conditional, and using an 
unconditional info_TEXINFOS=$(INFOFILES), but that didn't do what I 
expected either -- it sets PDFS to bdf.pdf unconditionally in Makefile.in.

I'd appreciate any suggestions!

Thanks,
- Brooks