Those macros are also defined by the compiler-provided float.h which
will be included later on (at least in the FreeBSD buildworld case) and
triggers these -Werror warnings. Including <float.h> first and only
defining the macros when DBL_DIG/FLT_DIG is missing fixes this problem.
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>
Closes#10864
417e646722