games/lwjgl3: Fix build in poudriere

compile:
[javac: compile @NullMarked] Compiling 1 source file to /wrkdirs/usr/ports/games/lwjgl3/work/lwjgl3-3.3.5/bin/classes/ant

BUILD FAILED
/wrkdirs/usr/ports/games/lwjgl3/work/lwjgl3-3.3.5/build.xml:454: /wrkdirs/usr/ports/games/lwjgl3/work/lwjgl3-3.3.5/bin/libs/java/jspecify.jar is read-only.

Reported by: pkg-fallout