Disable valgrind 32-bit x86. It does not like SSE.

Rationale:
We got a buildbot failure in ART on host-x86-valgrind after
enabling sse4.2 for hosts (which causes clang to use SSE
that is not recognized by valgrind32).

Bug: 63585550

Test: ./run_build_test_target.py art-gtest-valgrind32 completed.

Change-Id: Ic7ba4d1fd028ef39ddb002fcaa1b023595117cd3
diff --git a/test/testrunner/target_config.py b/test/testrunner/target_config.py
index baf7600..e8b6f1c 100644
--- a/test/testrunner/target_config.py
+++ b/test/testrunner/target_config.py
@@ -303,7 +303,8 @@
         }
     },
     'art-gtest-valgrind32': {
-        'make' : 'valgrind-test-art-host32',
+      # Disabled: x86 valgrind does not understand SSE4.x
+      # 'make' : 'valgrind-test-art-host32',
         'env': {
             'ART_USE_READ_BARRIER' : 'false'
         }