Make dex2oat(d) and hiddenapi 64-bit only on host.

Following https://r.android.com/1239726 we no longer need multilib host
dex2oat.

Also clean up a prefer32 device override that isn't applicable for the
host-only hiddenapi binary.

Test: m (with and without HOST_PREFER_32_BIT=true)
Test: art/build/apex/runtests.sh (with and without HOST_PREFER_32_BIT=true)
Test: lunch sdk-eng && art/tools/buildbot-build.sh --host && \
  art/test/run-test --host --optimizing 641-checker-arraycopy
  (with and without HOST_PREFER_32_BIT=true)
Bug: 148372405
Bug: 149749169
Change-Id: I46256ad7e8778e8d0f24b40d5acde482c4b66971
diff --git a/build/apex/art_apex_test.py b/build/apex/art_apex_test.py
index bc0de41..0e63afd 100755
--- a/build/apex/art_apex_test.py
+++ b/build/apex/art_apex_test.py
@@ -614,8 +614,7 @@
   def run(self):
     # Check binaries for ART.
     self._checker.check_executable('hprof-conv')
-    self._checker.check_symlinked_multilib_executable('dex2oat')
-    self._checker.check_symlinked_multilib_executable('dex2oatd')
+    self._checker.check_executable('dex2oatd')
 
     # Check exported native libraries for Managed Core Library.
     self._checker.check_native_library('libandroidicu-host')