iconv_open: non-gnu make fails to generate "iconv_open-aix.h"

[Assaf Gordon]

Hello,

While investigating some other issue, I noticed that non-gnu make
fails to create 'iconv_open-aix.h' from 'iconv_open-aix.gperf'.

Perhaps this is a non-issue, and only gnu-make is supported
for this bootstrapping stage (and non-gnu makes are only supported
after "make dist"). Still, worth reporting.

To reproduce:

   ./gnulib-tool --create-testdir --dir=foo iconv_open
   cd foo
   ./configure && make   ## gnu make - works OK

   ## gnu make - the "-aix.h" file is re-generated without problem
   rm gllib/iconv_open-aix.h
   make

   # now try again with BSD make
   $ rm gllib/iconv_open-aix.h
   $ bmake
   bmake  all-recursive
   Making all in gllib
   bmake[2]: don't know how to make iconv_open-aix.h. Stop

   bmake[2]: stopped in /home/gordon/projects/gnulib/foo/gllib
    *** Error code 1

The 'bmake' here is BSD-make from the stock Debian 'bmake' package,
but the same happens on FreeBSD.

-assaf