fix: Disable xapian tests

xapian has a long-ass test phase that takes multiple hours to complete

config/workarounds/default.nix

@@ -103,6 +103,10 @@ in
           sha256 = "09mvk9zxclkf4wrkkfzg0p2hx1f74gpymr0a0l3pckmk6za2n3d1";
         };
       });
+      xapian = prev.xapian.overrideAttrs
+        (old: {
+          testPhase = "true";
+        });
     })
   ];
 }