time logging for build targets is live

As described in Bug 287274 we are now logging real/user/system time
for most build targets in src/Makefile

You can see it in our CI system:

curl -sSf https://ci.freebsd.org/job/FreeBSD-main-armv7-build/lastBuild/consoleText
| grep '^>>> Time spent'
>>> Time spent on target buildworld: real 1969.50 user 34532.44 sys 1347.55
>>> Time spent on target buildkernel: real 156.47 user 2460.27 sys 320.05
>>> Time spent on target install: real 0.03 user 0.00 sys 0.03
>>> Time spent on target installconfig: real 0.02 user 0.00 sys 0.02
>>> Time spent on target distributeworld: real 186.72 user 125.05 sys 62.56
>>> Time spent on target installetc: real 38.47 user 31.50 sys 7.07
>>> Time spent on target packageworld: real 41.63 user 465.23 sys 9.17
>>> Time spent on target distributekernel: real 18.16 user 12.36 sys 5.79
>>> Time spent on target packagekernel: real 26.39 user 102.26 sys 1.73

-Wolfram

-- 
Wolfram Schneider <wosch@FreeBSD.org> https://wolfram.schneider.org