yosysSynthesisReport() should not hardcode the FuseSoC version

[oleg-nenashev]

The current usage pattern is:

                yosysSynthesisReport {
					core 'mor1kx'
					target 'synth'
					logPath 'build/mor1kx_5.0-r3/synth-icestorm/yosys.log'
				}

logPath should be explicitly set by a user, so their Jenkinsfiles will fall apart once the FuseSoC version changes in the LCCI Image (which is not even parameterizable). My suggestion would be to calculate a default log path inside the Pipeline step. If needed, we can expose version environment variables for tools in the LCCI images.