Fix missing entry for the static libdexfile_support test in the gtest list.

Also comment on the lack of test_per_src for those tests, and update the
find predicate in run-gtests.sh to handle these test binaries that end with
_tests instead of _test.

Bug: 123186083
Test: m test-art-host-gtest-art_libdexfile_support_tests
Test: m test-art-host-gtest-art_libdexfile_support_static_tests
Test: Buildbot style device test:
  art/tools/buildbot-build.sh -j8 --target && \
  art/tools/cleanup-buildbot-device.sh && \
  art/tools/setup-buildbot-device.sh && \
  art/tools/buildbot-sync.sh && \
  art/tools/run-gtests.sh
Change-Id: I2c103f760dde1154f44b1c90ff3ab9ae356d6318