timedate: use SymlinkFlags enum members for flags

The flags to pass to symlinkat_atomic_full are defined in the
SymlinkFlags enum type. The previous code passed the result of a boolean
check operation directly instead of using flags.

Be explicit about the value to pass instead of relying on true
corresponding to the enum value for the SYMLINK_MAKE_RELATIVE flag.

Signed-off-by: Daniel Wagenknecht <dwagenknecht@emlix.com>

src/timedate/timedated.c

@@ -312,7 +312,7 @@ static int context_write_data_timezone(Context *c) {
         }
 
         return symlinkat_atomic_full(source, AT_FDCWD, etc_localtime(),
-                                     !secure_getenv("SYSTEMD_ETC_LOCALTIME"));
+                                     !secure_getenv("SYSTEMD_ETC_LOCALTIME") ? SYMLINK_MAKE_RELATIVE : 0);
 }
 
 static const char* etc_adjtime(void) {