Improve environment setup. Fix Verilator installation process.
Created by: zchamski
- verif/sim/setup-env.sh: Double-quote variable values. Install Verilator in 'tools/verilator' by default. Add SPIKE_PATH to PATH.
- verif/regress/install-verilator.sh: By default use per-version dirs to build and install Verilator. Add and improve configuration messages.