Skip gtest ImgDiagTest.ImageDiffPidSelf when running tests on VM.

We do skip this test on host, as it tries to access system files for
which it does not have permissions. It's the same situation on VM.

Test: checked that ImgDiagTest.ImageDiffPidSelf is skipped on VM:
    . ./build/envsetup.sh
    lunch riscv64-trunk_staging-eng
    export SOONG_ALLOW_MISSING_DEPENDENCIES=true
    art/tools/buildbot-build.sh --target -j72

    export ART_TEST_SSH_USER=ubuntu
    export ART_TEST_SSH_HOST=localhost
    export ART_TEST_SSH_PORT=10001
    export ART_TEST_ON_VM=true

    . art/tools/buildbot-utils.sh
    art/tools/buildbot-cleanup-device.sh
    art/tools/buildbot-setup-device.sh
    art/tools/buildbot-sync.sh

    art/tools/run-gtests.sh \
        /apex/com.android.art/bin/art/riscv64/art_imgdiag_tests

Change-Id: If183439b2e9269ab199450fa12a1a0e0ef2e8dee
5 files changed