CI-unixish.yml: show check time for each file in selfcheck

[firewave]

The existing usage of --showtime=top5_summary is broken and also would not provide any context of which file the data belongs to.

[firewave]

If we were using a project this information could be used to order the files to process the slowest at first.

[firewave]

Files > 60 seconds:

Check time: lib/astutils.cpp: 87.222s
Check time: lib/checkclass.cpp: 106.768s
Check time: lib/checkother.cpp: 86.4929s
Check time: lib/checkstl.cpp: 84.4599s
Check time: lib/checkuninitvar.cpp: 72.8557s
Check time: lib/checkunusedvar.cpp: 88.7682s
Check time: lib/checkio.cpp: 322.58s
Check time: lib/templatesimplifier.cpp: 107.094s
Check time: lib/symboldatabase.cpp: 421.475s
Check time: lib/tokenize.cpp: 544.499s
Check time: cli/cmdlineparser.cpp: 1546.02s

[firewave]

If we were using a project this information could be used to order the files to process the slowest at first.

Won't actually help since cli/cmdlineparser.cpp is by far the longest running file and it is close to be one of the first being analyzed.