sudo: Compile mksigname and mksiglist for build host

sudo: Compile mksigname and mksiglist for build host

cross compiling sudo doesnt work well since it uses
mksigname and mksiglist to generate C sources which
are then used in sudo build itself. With this patch
now we make sure those hosttools are compiled for
build machine. It fixes the build failures like

./mksigname > signame.c
/bin/sh: ./mksigname: cannot execute binary file
make[1]: *** [signame.c] Error 126

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>