travis: Adding isl to be built.
travis: Adding isl to be built.

timvideos/conda-hdmi2usb-packages,litex-hub/litex-conda-eda,litex-hub/litex-conda-compilers,timvideos/conda-misoc-lm32,timvideos/conda-misoc-lm32,timvideos/conda-hdmi2usb-packages,litex-hub/litex-conda-prog