Add xgboost4j support FreeBSD

[huanghwh]

I use this command to build and test:

#!/bin/sh
cmake -B build -S . -GNinja \
  -DCMAKE_C_FLAGS="-I/usr/local/include" \
  -DCMAKE_CXX_FLAGS="-I/usr/local/include" \
  -DCMAKE_EXE_LINKER_FLAGS="-ldmlc -L/usr/local/lib" \
  -DCMAKE_SHARED_LINKER_FLAGS="-ldmlc -L/usr/local/lib -Wl,-s" \
  -DBUILD_WITH_SYSTEM_DMLC=ON -DJVM_BINDINGS=ON
cd build && ninja
export JAVA_HOME=/usr/local/openjdk17
cd ../jvm-packages && mvn install -DskipTests=true

[wbo4958]

@trivialfis @hcho3, would you help check it?

[Copilot]

Pull request overview

Adds FreeBSD as a supported platform for the XGBoost JVM bindings by teaching the Java native library loader and JNI packaging script to recognize and place FreeBSD native artifacts under the expected resource path.

Changes:

• Add FREEBSD to NativeLibLoader.OS and OS detection logic, and include a FreeBSD-specific OpenMP dependency hint on load failure.
• Update the JNI build/packaging script to copy the native library into a freebsd/<arch> resource directory.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/NativeLibLoader.java	Adds FreeBSD OS enum/detection and updates supported-OS docs + load-failure messaging.
jvm-packages/create_jni.py	Adds FreeBSD mapping so the built .so is copied into the correct freebsd resources folder.

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