JOEL4: check for the existence of tools

A new target has been added to the makefile called 'tools'. This new target
checks for the existence of the required tools before starting the build process.
Currently this target is not run by default, but is optional for the developer
to run at a convenient time.

Signed-off-by: Joel Nider <joel@nider.org>
JOEL4: use the LDFLAGS variable

The $(LDFLAGS) variable was not being used when $(LD) was called. This caused
an issue when building on a platform that was not 32-bit x86.

Signed-off-by: Joel Nider <joel@nider.org>
bug-fix: 22