Makefile: download firtool if it is not in PATH

[Tang-Haojin]

No description provided.

[XiangShanRobot]

[Generated by IPC robot]
commit: 41c15f2

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
41c15f2	1.868	0.491	2.158	1.202	2.902	2.160	1.412	0.874	1.436	1.103	3.622	2.639	2.280	3.136

master branch:

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
014ee79	1.868	0.491	2.158	1.202	2.902	2.160	1.413	0.874	1.436	1.103	3.622	2.615	2.280	3.136
fc00d28	1.880	0.491	2.158	1.196	2.906	2.163	1.415	0.882	1.436	1.104	3.646	2.652	2.279	3.155
084afb7	1.880	0.491	2.158	1.196	2.906	2.163	1.418	0.882	1.436	1.104	3.646	2.678	2.279	3.155
4e12f40	1.880	0.491	2.158	1.196	2.906	2.163	1.418	0.882	1.436	1.104	3.646	2.678	2.279	3.155
4b50637	1.880	0.491	2.158	1.196	2.906	2.163	1.418	0.882	1.436	1.104	3.646	2.678	2.279	3.155
ca82deb	1.867	0.491	2.158	1.197	2.890	2.169	1.418	0.883	1.436	1.111	3.646	2.678	2.278	3.184
9de7804	1.874	0.491	2.144	1.197	2.890	2.169	1.417	0.874	1.439	1.111	3.642	2.668	2.279	3.184
9eca914	1.874	0.491	2.144	1.192	2.890	2.169	1.420	0.874	1.445	1.111	3.655	2.686	2.279	3.184
0b8e1fd	1.874	0.491	2.144	1.192	2.890	2.169	1.420	0.874	1.445	1.111	3.655	2.686	2.279	3.184
2bf6e0e	1.866	0.491	2.144	1.192	2.890	2.169	1.419	0.874	1.439	1.111	3.655	2.678	2.279	3.184

[poemonsense]

fix #2392 before merge?

[XiangShanRobot]

[Generated by IPC robot]
commit: fab38bb

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
fab38bb	1.868	0.491	2.158	1.202	2.902	2.160	1.412	0.874	1.436	1.103	3.622	2.639	2.280	3.136

master branch:

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
3711cf3			2.158	1.202			1.412	0.874	1.436			2.615		3.136
014ee79	1.868	0.491	2.158	1.202	2.902	2.160	1.413	0.874	1.436	1.103	3.622	2.615	2.280	3.136
fc00d28	1.880	0.491	2.158	1.196	2.906	2.163	1.415	0.882	1.436	1.104	3.646	2.652	2.279	3.155
084afb7	1.880	0.491	2.158	1.196	2.906	2.163	1.418	0.882	1.436	1.104	3.646	2.678	2.279	3.155
4e12f40	1.880	0.491	2.158	1.196	2.906	2.163	1.418	0.882	1.436	1.104	3.646	2.678	2.279	3.155
4b50637	1.880	0.491	2.158	1.196	2.906	2.163	1.418	0.882	1.436	1.104	3.646	2.678	2.279	3.155
ca82deb	1.867	0.491	2.158	1.197	2.890	2.169	1.418	0.883	1.436	1.111	3.646	2.678	2.278	3.184
9de7804	1.874	0.491	2.144	1.197	2.890	2.169	1.417	0.874	1.439	1.111	3.642	2.668	2.279	3.184
9eca914	1.874	0.491	2.144	1.192	2.890	2.169	1.420	0.874	1.445	1.111	3.655	2.686	2.279	3.184
0b8e1fd	1.874	0.491	2.144	1.192	2.890	2.169	1.420	0.874	1.445	1.111	3.655	2.686	2.279	3.184

[Tang-Haojin]

fix #2392 before merge?

Done~