comptools: do not force build of make-3.81 unless really needed

On systems with make-3.82, we forcibly force the build and the use
of make-3.81

But some newer tools break when building with make-3.81. For example,
eglibc-3.18 breaks.

Introduce a new blind options that tools may select if they require
make-3.81. If the system does not have make-3.81, and this option is
selected, then we force the build of make-3.81. Otherwise, we leave
it to the user to decide on his own.

Note that no component selects this option for now. It will come in
later patches as we find them.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 diff -dur binutils-2.17.old/bfd/opncls.c binutils-2.17/bfd/opncls.c

 --- binutils-2.17.old/bfd/opncls.c	2006-03-16 13:20:16.000000000 +0100

 +++ binutils-2.17/bfd/opncls.c	2007-05-01 18:26:11.000000000 +0200

 @@ -158,6 +158,13 @@

  {

    bfd *nbfd;

    const bfd_target *target_vec;

 +  struct stat s;

 +

 +  if (stat (filename, &s) == 0)

 +    if (S_ISDIR(s.st_mode)) {

 +      bfd_set_error (bfd_error_file_not_recognized);

 +      return NULL;

 +    }

    nbfd = _bfd_new_bfd ();

    if (nbfd == NULL)