If you downloaded the Ubuntu version
sage-9.0-Ubuntu_18.04-i686
from the download-linux page on the SageMath website,
you don't need to run `make`, it should be ready to use.
If you want to build from source, you should
- download the source file, preferrably for the latest
development version, currently SageMath 9.1.rc0
- install the prerequisites listed at
- run
make configure
./configure
- follow the recommendations at the end of that stage
(it might suggest installing a few more system packages)
- then run
make -s V=0