##### http://autoconf-archive.cryp.to/patch_libtool_to_add_host_cc.html
#
# OBSOLETE MACRO
#
#   The problem is fixed in modern libtool versions.
#
# SYNOPSIS
#
#   PATCH_LIBTOOL_TO_ADD_HOST_CC
#
# DESCRIPTION
#
#   The libtool 1.4.x processing (and patched 1.3.5) uses a little
#   "impgen" tool to turn a "*.dll" into an import "*.lib" as it is
#   needed for win32 targets. However, this little tool is not shipped
#   by binutils, it is not even a command option of dlltool or dllwrap.
#   It happens to be a C source snippet implanted into the libtool
#   sources - it gets written to ".libs", compiled into a binary
#   on-the-fly, and executed right away on the "dll" file to create the
#   import-lib (dll.a files in gcc-speak).
#
#   This mode works fine for a native build within mingw or cygwin, but
#   it does not work in cross-compile mode since CC is a crosscompiler
#   - it will create an .exe file on a non-win32 system, and as a
#   result an impgen.exe is created on-the-fly that can not be executed
#   on-the-fly. Luckily, the actual libtool snippet uses HOST_CC to
#   compile the sources which has a fallback to CC when the HOST_CC
#   variable was not set.
#
#   this ac-macro is trying to detect a valid HOST_CC which is not a
#   cross-compiler. This is done by looking into the $PATH for a "cc"
#   and the result is patched into libtool a HOST_CC, iow it adds
#   another configured variable at the top of the libtool script.
#
#   In discussions on the libtool mailinglist it occurred that later
#   gcc/binutils generations are able to link with dlls directly, i.e.
#   there is no import-lib needed anymore. The import-table is created
#   within the linker itself (in-memory) and bound to the .exe/.dll
#   currently in the making. The whole stuff of impgen exe and
#   compiling it on-the-fly, well, it is superflouos then.
#
#   Since mingw crosscompilers tend to be quite a fresh development it
#   was agreed to remove the impgen stuff completly from libtool
#   sources. Still however, this macro does not hurt since it does not
#   patch impgen cmds but it just adds HOST_CC which might be useful in
#   other cross-compiling cases as well. Therefore, you can leave it in
#   for maximum compatibility and portability.
#
# LAST MODIFICATION
#
#   2006-10-13
#
# COPYLEFT
#
#   Copyright (c) 2006 Guido U. Draheim <guidod@gmx.de>
#
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AC_DEFUN([PATCH_LIBTOOL_TO_ADD_HOST_CC],
[# patch libtool to add HOST_CC sometimes needed in crosscompiling a win32 dll
if grep "HOST_CC" libtool >/dev/null; then
  if test "$build" != "$host" ; then
    if test "_$HOST_CC" = "_" ; then
      HOST_CC="false"
      for i in `echo $PATH | sed 's,:, ,g'` ; do
      test -x $i/cc && HOST_CC=$i/cc
      done
    fi
AC_MSG_RESULT(patching libtool to add HOST_CC=$HOST_CC)
    test -f libtool.old || (mv libtool libtool.old && cp libtool.old libtool)
    sed -e "/BEGIN.*LIBTOOL.*CONFIG/a\\
HOST_CC=$HOST_CC" libtool >libtool.new
    (test -s libtool.new || rm libtool.new) 2>/dev/null
    test -f libtool.new && mv libtool.new libtool # not 2>/dev/null !!
    test -f libtool     || mv libtool.old libtool
  fi
fi
])