`make buildkernel' 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 buildkernel' target should display the build time in seconds

[cem]

Thanks. Please re-upload with context. You can either use arc diff --create or simply generate a patch with huge amounts of context ([git] diff -U999999).

[wosch]

I updated the patch to cleanup the time temp file after build.

[emaste]

See also D13911. I like @bdrewery's suggestion that avoids needing a temp file.

[wosch]

In D13910#295268, @emaste wrote:

See also D13911. I like @bdrewery's suggestion that avoids needing a temp file.

I would love to get rid of the the temp file. However, it is not easy as it sounds.

The timestamp needs to be stored in a global Makefile variable, and changed when the targets actually runs, not when we start the make command. The variable needs to be changed from a sub-shell, and later read by a another sub-shell. The whole point of a subshell is that it doesn't affect the calling session.

A temp file in this case is the simple solution.

[wosch]

The updated patch works without a temp file.

Note: there is a small semantic change. We display the time in seconds for all kernels build, not per kernel. For most users this is a non-issue, because they usually build only one kernel at a time.

[cem]

Thanks, LGTM