java/openjdk17: fix build with clang 19

Clang 19 has a number of new warnings, and because java/openjdk17
compiles with -Werror by default, it results in errors similar to:

/wrkdirs/usr/ports/java/openjdk17/work/jdk17u-jdk-17.0.12-7-1/src/hotspot/os/posix/signals_posix.cpp:1681:20: error: cast from 'void (*)(int, siginfo_t *, ucontext_t *)' (aka 'void (*)(int, __siginfo *, __ucontext *)') to 'void (*)(int)' converts to incompatible function type [-Werror,-Wcast-function-type-mismatch]
 1681 |   act.sa_handler = (void (*)(int)) SR_handler;
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~

I propose to disable warnings-as-errors for this port, similar to what
is already done for openjdk8 and openjdk11. It does not make sense to
have this on by default, unless you are an upstream maintainer.

PR: 280561
Approved by: glewis (maintainer)
MFH: 2024Q3

(cherry picked from commit 4c37f9f5f253a5701fa94ddfc00520889bca9ea4)