Fallback to the next file location if the current location for .pdfbox.cache is not writable.
Currently there is a fallback from pdfbox.fontcache to user.home to java.io.tmpdir as directory to write .pdfbox.cache, but this is only on the level of if the system property is defined.
It would be nice to fallback to the next directory if the file is not writable in a directory.
Without config and on a system where user.home is not writable pdfbox is quite slow, as the caching is tried each time.
Usually java.io.tmpdir is writable, so this would provide better performance out of the box.
The workaound is to configure the pdfbox.fontcache system property.