Don't run 175-alloc-big-bignums for prebuild config

Prebuild configs use profiles that do not include key methods for
BigInteger so do not run for now:

* Ljava/math/BigInteger;->add([IJ)[I
* Ljava/math/BigInteger;->add([I[I)[I
* Ljava/math/BigInteger;->subtract([IJ)[I

Bug: 174470490
Test: art/test/testrunner/testrunner.py --32 -j1 --verbose --host -t 175
Change-Id: Ibb25c06a5633218bdac9509aed47ba8d744a9c53
diff --git a/test/knownfailures.json b/test/knownfailures.json
index f3f59bf..6588b49 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -1318,7 +1318,8 @@
     },
     {
         "tests": ["175-alloc-big-bignums"],
-        "variant": "interpreter | interp-ac | trace | no-image | debuggable",
+        "variant": "interpreter | interp-ac | trace | no-image | debuggable | prebuild",
+        "bug": "b/174470490",
         "description": "Interpreting BigInteger.add() is too slow (timeouts)"
     },
     {