Difftest: emu explicitly pass seed to verilator with Verilated::randSeed

[klin02]

Submodule PR #128
With Verilated::randSeed, we can truly pass seed to Verilator. Otherwise, seeds specified using srand48 will be overwritten by verilator's built-in srand48.
See more details in Verilator-doc "+verilator+rand+seed" and https://github.com/verilator/verilator/blob/master/include/verilated.cpp

[XiangshanBot]

[Generated by IPC robot]
commit: 6d97ef0

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
6d97ef0	1.847	0.489	2.070	1.151	2.830	2.078	1.397	0.793	1.397	1.104	3.587	2.659	2.273	2.819

master branch:

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
21bd600	1.847	0.489	2.070	1.151	2.830	2.078	1.397	0.793	1.397	1.104	3.587	2.659	2.273	2.819
0e8170d	1.847	0.489	2.070	1.151	2.830	2.078	1.398	0.793	1.397	1.104	3.587	2.656	2.273	2.819
adc0b8d	1.847	0.489	2.070	1.151	2.830	2.078	1.398	0.793	1.397	1.104	3.587	2.656	2.273	2.819
87433ba	1.847	0.489	2.070	1.151	2.830	2.078	1.398	0.793	1.397	1.104	3.587	2.656	2.273	2.819
4b2a95e	1.847	0.489	2.070	1.151	2.830	2.078	1.398	0.793	1.397	1.104	3.587	2.657	2.273	2.819
9ebbb51	1.847	0.489	2.070	1.151	2.830	2.078	1.398	0.793	1.397	1.104	3.587	2.664	2.273	2.819
8088cde	1.847	0.489	2.070	1.151	2.830	2.078	1.398	0.793	1.397	1.104	3.587	2.655	2.273	2.819
7b8f8f0	1.860	0.489	2.086	1.151	2.825	2.070	1.396	0.791	1.380	1.111	3.615	2.673	2.273	2.821
7fce807	1.849	0.489	2.100	1.154	2.828	2.073	1.396	0.782	1.395	1.103	3.603	2.660	2.274	2.805
5a9297b	1.867	0.489	2.078	1.167	2.815	2.095	1.397	0.793	1.395	1.098	3.599	2.655	2.271	2.822