Allow using ash as the shell for ./configure and make.
After an idea by "Martin Guy" <martinwguy@yahoo.it>:
http://sourceware.org/ml/crossgcc/2008-08/msg00037.html

/trunk/scripts/crosstool.sh | 4 4 0 0 ++++
/trunk/config/global/build-behave.in | 14 14 0 0 ++++++++++++++
2 files changed, 18 insertions(+)

 # x86_64 specific options

 config ARCH_x86_64

     select ARCH_SUPPORT_ARCH

     select ARCH_SUPPORT_CPU

     select ARCH_SUPPORT_TUNE

     help

       The x86_64 architecture, as defined by:

         http://www.amd.com/us-en/Processors/DevelopWithAMD/0,,30_2252_875_7044,00.html