This fixes compile warnings which show up when we build with
-Dtracker_core=subproject. This is an example of the kind of
warning:

    [7/186] Compiling C object 'subprojects/tracker/src/tracker-store/7bb4675@@tracker-store@exe/tracker-config.c.o'.
    In file included from ../subprojects/tracker/src/tracker-store/tracker-config.c:21:
    subprojects/tracker/./config.h:25: warning: "GETTEXT_PACKAGE" redefined
       25 | #define GETTEXT_PACKAGE "tracker"
          |
    In file included from <command-line>:
    ./config.h:25: note: this is the location of the previous definition
       25 | #define GETTEXT_PACKAGE "tracker-miners"
          |