The option -o can be used to set the output file name. It defaults to urbiengine-HOST-CORE when building engines, and uobject-HOST.a when building libraries.

$ ls
foo.cc foo.hh
$ umake --core webots -o urbi

/usr/local/gostai/core/linux/libtool --tag=CXX --mode=compile g++ -O2
-pthread -I/usr/local/gostai/core/include -c foo.cc -o foo.lo g++ -O2
-pthread -I/usr/local/gostai/core/include -c foo.cc -o foo.o
/usr/local/gostai/core/linux/libtool --mode=link --tag=CXX g++ -O2
-pthread -L/usr/local/gostai/core/linux/webots -o
urbiengine-linux-webots ./foo.o
/usr/local/gostai/core/linux/webots/*.la libtool: link: warning:
library `/usr/local/gostai/core/linux/webots/liburbicore.la' was
moved.  libtool: link: warning: library
`/usr/local/gostai/core/linux/webots/liburbicore.la' was moved.  g++
-O2 -pthread -o urbiengine-linux-webots ./foo.o
-L/usr/local/gostai/core/linux/webots
/usr/local/gostai/core/linux/webots/liburbicore.a
-L/tmp/urbi/gostai/core/linux/webots
-L/tmp/urbi/gostai/kernel/linux/engine -L/usr/local/webots/lib
-lController

$ ls
foo.cc foo.hh foo.lo foo.o urbi