Replace the individual TARGET_*=y lines with TARGET_ARCH,
similar to how TARGET_BASE_ARCH is handled already.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The config-target.mak files are small constant, we can therefore just
write them down explicitly.
This removes a pretty large part of the configure script, including the
whole logic to detect which accelerators are supported by each target.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>