Disable build of ivshmem on non-KVM systems

Signed-off-by: Cam Macdonell <cam@cs.ualberta.ca>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

Makefile.target

@@ -191,7 +191,7 @@ obj-y += rtl8139.o
 obj-y += e1000.o
 
 # Inter-VM PCI shared memory
-obj-y += ivshmem.o
+obj-$(CONFIG_KVM) += ivshmem.o
 
 # Hardware support
 obj-i386-y += vga.o