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 -ru gdb-6.8.orig/bfd/sysdep.h gdb-6.8/bfd/sysdep.h

 --- gdb-6.8.orig/bfd/sysdep.h	2007-07-03 16:26:42.000000000 +0200

 +++ gdb-6.8/bfd/sysdep.h	2011-08-21 13:33:47.000000000 +0200

 @@ -131,7 +131,7 @@

  extern PTR realloc ();

  #endif

 -#if !HAVE_DECL_STPCPY

 +#if !HAVE_DECL_STPCPY && !defined(stpcpy)

  extern char *stpcpy (char *__dest, const char *__src);

  #endif