test/unittest: initilize ztimer64 is required, use xtimer test-fib

test-fib has direct use of xtimer -> it needs to use the module

tests/unittests/main.c

@@ -31,6 +31,11 @@ int main(void)
     ztimer_init();
 #endif
 
+#if MODULE_ZTIMER64_USEC || MODULE_ZTIMER64_MSEC || MODULE_ZTIMER64_SEC
+    /* auto_init is disabled, but some modules depends on this module being initialized */
+    ztimer64_init();
+#endif
+
 #if IS_USED(MODULE_XTIMER) && !IS_USED(MODULE_ZTIMER_XTIMER_COMPAT)
     /* auto_init is disabled, but some modules depends on this module being initialized */
     xtimer_init();

tests/unittests/tests-fib/Makefile.include

@@ -1,3 +1,3 @@
 CFLAGS += -DFIB_DEVEL_HELPER -DUNIVERSAL_ADDRESS_SIZE=16 -DUNIVERSAL_ADDRESS_MAX_ENTRIES=40
 
-USEMODULE += fib
+USEMODULE += fib xtimer