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 -durN gcc-3.4.6.orig/gcc/config/rs6000/linux-unwind.h gcc-3.4.6/gcc/config/rs6000/linux-unwind.h

 --- gcc-3.4.6.orig/gcc/config/rs6000/linux-unwind.h	2005-03-17 11:41:18.000000000 +0100

 +++ gcc-3.4.6/gcc/config/rs6000/linux-unwind.h	2007-08-15 23:07:00.000000000 +0200

 @@ -32,6 +32,7 @@

     these structs elsewhere;  Many fields are missing, particularly

     from the end of the structures.  */

 +#ifndef inhibit_libc

  struct gcc_vregs

  {

    __attribute__ ((vector_size (16))) int vr[32];

 @@ -320,3 +321,4 @@

  									\

      goto SUCCESS;							\

    } while (0)

 +#endif