libobs: Fix disk space reporting for attached network drives on macOS

While the NSURLVolumeAvailableCapacityForOpportunisticUsageKey resource
correctly reports available disk space for local volumes (regardless
of actual file system used), it does not report actual values for
attached network drives.

The NSURLVolumeAvailableCapacityKey resource will still report
available disk space as expected, so use this value for non-local
volumes instead.

libobs/util/platform-cocoa.m

@@ -363,10 +363,21 @@ int64_t os_get_free_space(const char *path)
     if (path) {
         NSURL *fileURL = [NSURL fileURLWithPath:@(path)];
 
-        NSDictionary *values = [fileURL resourceValuesForKeys:@[NSURLVolumeAvailableCapacityForOpportunisticUsageKey]
-                                                        error:nil];
+        NSDictionary *values = [fileURL resourceValuesForKeys:@[NSURLVolumeIsLocalKey] error:nil];
 
-        NSNumber *availableSpace = values[NSURLVolumeAvailableCapacityForOpportunisticUsageKey];
+        BOOL isLocalVolume = [values[NSURLVolumeIsLocalKey] boolValue];
+
+        NSURLResourceKey volumeKey;
+
+        if (isLocalVolume) {
+            volumeKey = NSURLVolumeAvailableCapacityForOpportunisticUsageKey;
+        } else {
+            volumeKey = NSURLVolumeAvailableCapacityKey;
+        }
+
+        values = [fileURL resourceValuesForKeys:@[volumeKey] error:nil];
+
+        NSNumber *availableSpace = values[volumeKey];
 
         if (availableSpace) {
             return availableSpace.longValue;