Fix UnsupportedOperationException on Windows in JNI* loaders

[philwalk]

Problem

On Windows (NTFS), JNIBLAS, JNILAPACK, and JNIARPACK all crash during initialisation with:

java.lang.UnsupportedOperationException: 'posix:permissions' not supported as initial attribute

This is thrown by Files.createTempFile(prefix, suffix, PosixFilePermissions.asFileAttribute(...)) because NTFS does not support POSIX file attributes. The exception is caught by the InstanceBuilder fallback chain, so on Windows the JNI native backend silently never loads and every caller falls
back to the pure-Java implementation.

Root cause

Three places in the code unconditionally pass a POSIX FileAttribute to Files.createTempFile:

• blas/src/main/java/dev/ludovic/netlib/blas/JNIBLAS.java
• lapack/src/main/java/dev/ludovic/netlib/lapack/JNILAPACK.java
• arpack/src/main/java/dev/ludovic/netlib/arpack/JNIARPACK.java

Fix

Guard the attribute with a FileSystems.getDefault().supportedFileAttributeViews().contains("posix") check — the same portable idiom used elsewhere in the JDK ecosystem. On non-POSIX filesystems (Windows/NTFS) this returns an empty FileAttribute<?>[], which Files.createTempFile accepts fine.

Also adds the existing macOS pattern of os.name normalisation and .dll extension for Windows, so the correct resource path resources/native/windows-amd64/libnetlibblasjni.dll is resolved when a Windows native DLL is bundled in the JAR.

Testing

Verified on Windows 11 / MSYS2 / JVM 21 with Breeze 2.1.0:

• Before: JNIBLAS: 'posix:permissions' not supported as initial attribute → falls back to VECTORAPIBLAS
• After: INFO: Using dev.ludovic.netlib.blas.JNIBLAS → native OpenBLAS loaded

Relates to #20.

[luhenry]

I’m surprised this works even with the change given that it’s still missing the native JNI shim that sits between the Java code and the native library (the jni.c files for each of blas, lapack, arpack).

Would you be interested in adding support for Windows on CI as well? I can always ask Claude otherwise.

[philwalk]

I compiled the native shim for my testing.
We use netlib for benchmarking uni.MatD against breeze.

Although netlib is 50% faster than org.bytedeco" % "openblas-platform" (on 512x512 matrix multiply), it's not as user-friendly without a bundled native dll.

Happy to help out if I can ...

[luhenry]

Let's merge it as-is for now, and we can work on having the native wrapper in a follow up PR

[philwalk]

Would you be interested in adding support for Windows on CI as well? I can always ask Claude otherwise.

Let me know if this isn't what you require: #39