gnulib-tool: fix GNU sed recognition

[Bruno Haible]

Hi,

The test whether 'sed' supports the --posix option was broken: On MacOS X,
"/usr/bin/sed --posix d" succeeds.


2007-01-21  Bruno Haible  <address@hidden>

        * gnulib-tool: Fix test whether sed is GNU sed supporting --posix.

*** gnulib-tool 17 Jan 2007 23:46:34 -0000      1.216
--- gnulib-tool 21 Jan 2007 20:03:10 -0000
***************
*** 71,77 ****
  # However, do this only for gnulib-tool itself, not for the code that
  # gnulib-tool generates, since we don't want "sed --posix" to leak
  # into makefiles.
! if (alias) > /dev/null 2>&1 && echo | sed --posix d >/dev/null 2>&1; then
    alias sed='sed --posix'
  fi
  
--- 71,77 ----
  # However, do this only for gnulib-tool itself, not for the code that
  # gnulib-tool generates, since we don't want "sed --posix" to leak
  # into makefiles.
! if (alias) > /dev/null 2>&1 && echo | sed --posix -e d >/dev/null 2>&1; then
    alias sed='sed --posix'
  fi