`make buildworld' should display the build time in seconds

[wosch]

Summary

As described in https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=224433

the top level `make buildworld' target should display the build time in seconds

[imp]

This looks good in principle, modulo some nits. I'd let Bryan have the final say, but commit it if he says nothing.

Makefile.inc1

968

A fixed name is bad. It's also bad that it's in the makeworld tree. Consider something in /tmp/

973

You never remove this file. You should.

981

I'd use "built" rather than "build" because it describes something that went on in the past (even though it just finished).

[bdrewery]

You can also just record the time the build starts with something like this:

.if !defined(_BUILDWORLD_START)
_BUILDWORLD_START!= date +%s
.export _BUILDWORLD_START
.endif

Then compare its value in buildworld_epilogue, no tmpfile needed.

[wosch]

The updated patch works without a temp file.