.mk file so they can be reused.
Introduce a new option, CRUNCH_BUILDTOOLS, which lists the binaries that
require tools built in the local architecture. sh and csh both require this.
It was previously hardcoded in rescue/rescue/Makefile .
Introduce a new option, CRUNCH_SHLIBS, which lists the shared libraries
to link against. These override the static libraries listed in CRUNCH_LIBS.
Some build environments may wish to use a handful of shared libraries
(eg libc.so) so other small, dynamic binaries can be run in the environment.
Remove the now-shared code from rescue/rescue/Makefile and introduce the
CRUNCH_BUILDTOOLS option for the above shells.
