symbiflow: get critical path timings
symbiflow: get critical path timings

Signed-off-by: Karol Gugala <38af71640571ee4b5093d4f69ffca1ac454f2948@antmicro.com>

SymbiFlow/fpga-tool-perf,SymbiFlow/fpga-tool-perf,SymbiFlow/fpga-tool-perf,SymbiFlow/fpga-tool-perf