Revert "Use 32 or 64 bit dex2oat explicitly depending on HOST_PREFER_32_BIT."

This reverts commit 8aa6a82003ce7ece4511996341021e7084d40b3a.

Reason for revert: Original issue is fixed by
https://android-review.googlesource.com/c/platform/art/+/1239726

Test: art/tools/buildbot-build.sh --host \
        && art/test/testrunner/testrunner.py --host --optimizing \
             -t 640-checker-integer-valueof
Bug: 149749169
Bug: 155861770
Change-Id: I77d2c1c66fb91b079452f29c40dfce26e7224f8a
Merged-In: I77d2c1c66fb91b079452f29c40dfce26e7224f8a
(cherry picked from commit 15c622d385ec46b4fc236b7445d016bc2ad699ef)