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>

 --- gcc/gcc/config.gcc.uclibc100-sh~	2006-03-06 20:46:56 +0100

 +++ gcc/gcc/config.gcc	2006-03-10 15:02:41 +0100

 @@ -1905,7 +1905,7 @@

  	;;

  sh-*-elf* | sh[12346l]*-*-elf* | sh*-*-kaos* | \

  sh-*-symbianelf* | sh[12346l]*-*-symbianelf* | \

 -  sh-*-linux* | sh[346lbe]*-*-linux* | \

 +  sh*-*-linux* | sh[346lbe]*-*-linux* | \

    sh-*-netbsdelf* | shl*-*-netbsdelf* | sh5-*-netbsd* | sh5l*-*-netbsd* | \

     sh64-*-netbsd* | sh64l*-*-netbsd*)

  	tmake_file="${tmake_file} sh/t-sh sh/t-elf"