Update OnnxRuntime.java for OS X environment. (#3985)
onnxruntime init failure due to wrong path of reading native libraries. In OS X 64 system, the arch name is detected as x86 which generates invalid path to read native libraries.
Exception java.lang.UnsatisfiedLinkError: no onnxruntime in java.library.path
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1867)
at java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary(System.java:1122)
at ai.onnxruntime.OnnxRuntime.load(OnnxRuntime.java:174)
at ai.onnxruntime.OnnxRuntime.init(OnnxRuntime.java:81)
at ai.onnxruntime.OrtEnvironment.<clinit>(OrtEnvironment.java:24)
