Trouble with gnulib/float.h on Intrepid

[Rhys Ulerich]

On Intrepid, a BG/P system up at Argonne with some fun old IBM XL
compilers, a user of mine is seeing gnulib/float.h containing the line
    #include " "
which appears to be arising from
    configure:13477: checking absolute name of <float.h>
    configure:13516: result: ""
due to 
http://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob_plain;f=m4/float_h.m4
where
    host_cpu='powerpc64'
    host_os='linux-gnu'
    host_vendor='unknown'

What information might I collect to help debug this?  This is atop
gnulib HEAD.  I have a full config.log sitting around and would be
happy to send it someone's way in addition to the generated configure
file.

- Rhys