build: Always enable debugging logging

We shouldn't need to specifically enable debug logging to get useful
data out of a compiled libfprint either, so always enable debugging
output. It will still be switched off at runtime, by default.

meson_options.txt

@@ -14,10 +14,6 @@ option('x11-examples',
        description: 'Whether to build X11 example applications',
        type: 'boolean',
        value: true)
-option('debug_log',
-       description: 'Debug message logging',
-       type: 'boolean',
-       value: false)
 option('doc',
        description: 'Whether to build the API documentation',
        type: 'boolean',