Fix symbolic file(or contains symbolic directory) check condition

[devjeonghwan]

file.getCanonicalFile() is not solve symbolic link in Windows environment (See issue)

So i change to more precise method toRealPath().

[saudet]

Let's replace all the calls, not just that one. However, Path.toRealPath() doesn't appear available before Android 8.0:
https://developer.android.com/reference/java/nio/file/Path?hl=ro#toRealPath(java.nio.file.LinkOption...)
So let's create our own Loader.getCanonicalFile() that calls Path.toRealPath() only on Windows, and File.getCanonicalFile() on other platforms.

[devjeonghwan]

I tested on Android 25 API Level.

[devjeonghwan]

Frequently compare platform string to "windows" seems slow... How about implementing a one-time check(consider volatile or syncronoized) or enum for platform?

[saudet]

We can use something like private static final boolean WINDOWS = PLATFORM.startsWith("windows"); under this line:
https://github.com/bytedeco/javacpp/blob/master/src/main/java/org/bytedeco/javacpp/Loader.java#L82

BTW, there are other places in the code where File.getCanonicalPath() gets called:
https://github.com/bytedeco/javacpp/search?q=getCanonicalPath

[devjeonghwan]

We can use something like private static final boolean WINDOWS = PLATFORM.startsWith("windows"); under this line: https://github.com/bytedeco/javacpp/blob/master/src/main/java/org/bytedeco/javacpp/Loader.java#L82

BTW, there are other places in the code where File.getCanonicalPath() gets called: https://github.com/bytedeco/javacpp/search?q=getCanonicalPath

@saudet How about like this?

    /** Value created out of "java.vm.name", "os.name", and "os.arch" system properties.
     *  Returned by {@link #getPlatform()} and initialized with {@link Detector#getPlatform()}. */
    private static final String PLATFORM = Detector.getPlatform();

    /**
     * Returned an enumeration of known operating systems and initialized with {@link Detector#getOperatingSystem()}.
     */
    private static final Detector.OperatingSystem OPERATING_SYSTEM = Detector.getOperatingSystem();

    public static class Detector {
        public enum OperatingSystem {
            WINDOWS, LINUX, ANDROID, MACOSX, IOS, OTHER;

            /**
             * @return Parsed pre-defined operating system enum
             */
            static OperatingSystem parse(String string) {
                if (string != null){
                    string = string.toLowerCase();

                    if (string.startsWith("windows")) {
                        return OperatingSystem.WINDOWS;
                    } else if (string.startsWith("linux")) {
                        return OperatingSystem.LINUX;
                    } else if (string.startsWith("android")) {
                        return OperatingSystem.ANDROID;
                    } else if (string.startsWith("macosx")) {
                        return OperatingSystem.MACOSX;
                    } else if (string.startsWith("ios")) {
                        return OperatingSystem.IOS;
                    }
                }

                return OperatingSystem.OTHER;
            }
        }

        public static OperatingSystem getOperatingSystem(){
            return OperatingSystem.parse(Detector.getPlatform());
        }
        ...
    }

I think it's better than making a field just for windows.

[saudet]

No, let's just leave it as a string. That just adds unnecessary complexity.