I haven't received this yet, but read from the archive:
https://www.redhat.com/archives/libguestfs/2009-November/msg00268.html
The only suspicious part is the trailing ".c" on the command below:
+$(libsrcdir)/guestfs_protocol.c: force
+ $(MAKE) -C $(libsrcdir) guestfs_protocol.c
+$(libsrcdir)/guestfs_protocol.h: force
+ $(MAKE) -C $(libsrcdir) guestfs_protocol.c
Shouldn't that be .h?