RFR: 8368565: Adjust comment regarding dependency of libjvm.so to librt

[David Holmes]

On Wed, 24 Sep 2025 15:30:27 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> We have a legacy dependency of libjvm to librt for the` clock_*` functions :
> https://github.com/openjdk/jdk/blob/f993f90c86f89eb0c7f42ebecb45a68eae0bd9ea/make/autoconf/libraries.m4#L139
> 
> But this is for very old systems with distros like RHEL 6 or SLES11 with glibc 2.16 or older, where the clock_ functions were still in librt ; but those ancient distros play no role any more for current JDK26.
> On the other hand, we now use the `timer_*` functions from librt e.g. in JFR and these are _really_  in librt so the comment should be adjusted.

Changes requested by dholmes (Reviewer).

make/autoconf/libraries.m4 line 141:

> 139:   # librt
> 140:   if test "x$OPENJDK_TARGET_OS" = xlinux; then
> 141:     # Needed for the timer_* functions from librt used in JFR

It isn't just JFR - CompilerThreadTimeout also uses timers. I suggest just one comment at line 139 "#librt - for timers".

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PR Review: https://git.openjdk.org/jdk/pull/27473#pullrequestreview-3265452716
PR Review Comment: https://git.openjdk.org/jdk/pull/27473#discussion_r2377578541