I noticed that build/$confname/configure.log was truncated on some of my build nodes. Turns out, we are moving configure.log from tree root to that place a bit prematurely.

We move `configure.log` here:
https://github.com/openjdk/jdk/blob/4f194f10a1481cdc9df4e6338f6cabd07a34c84c/make/autoconf/basic.m4#L594-L618

...and that is called here:
https://github.com/openjdk/jdk/blob/4bcb8f04ed3623da7c84dda28017f473cbc97e53/make/autoconf/configure.ac#L316

Or, before we print configuration summary.

Now, this works most of the time by accident: when root dir and build dir are on the same filesystem, the file move does not interfere with inodes/FDs, and we are still able to write to the same file _after_ we moved. But if build dir is on _another_ filesystem, then we miss writing the configuration summary when file moves away.

Apparently, my systems fall into that trap, since build dir is on RAM disk.