This appears to be random test flake, though no common.

trunks-0.0.1-r1535: >>> Source compiled.
trunks-0.0.1-r1535: /build/gru/tmp/portage/chromeos-base/trunks-0.0.1-r1535/work/trunks-0.0.1/platform2/common-mk/platform2_test.py --action=pre_test --sysroot=/build/gru -- 
trunks-0.0.1-r1535: ERROR: ld.so: object 'libsandbox.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.
trunks-0.0.1-r1535: ........Invalid format for first line: bad_data

...<snip>...

trunks-0.0.1-r1535: [ RUN      ] BackgroundTransceiverTest.Synchronous
trunks-0.0.1-r1535: [FATAL:weak_ptr.cc(20)] Check failed: sequence_checker_.CalledOnValidSequencedThread() || HasOneRef(). WeakPtrs must be invalidated on the same sequenced thread.
trunks-0.0.1-r1535: 
trunks-0.0.1-r1535: qemu: uncaught target signal 6 (Aborted) - core dumped
trunks-0.0.1-r1535: Error: /var/cache/portage/chromeos-base/trunks/out/Default/trunks_testrunner: failed with signal SIGIOT|SIGABRT(6)
trunks-0.0.1-r1535:  * ERROR: chromeos-base/trunks-0.0.1-r1535::chromiumos failed (test phase):
trunks-0.0.1-r1535:  *   (no error message)
trunks-0.0.1-r1535:  * 
trunks-0.0.1-r1535:  * Call stack:
trunks-0.0.1-r1535:  *     ebuild.sh, line   93:  Called src_test
trunks-0.0.1-r1535:  *   environment, line 3873:  Called platform_src_test
trunks-0.0.1-r1535:  *   environment, line 3453:  Called platform_pkg_test
trunks-0.0.1-r1535:  *   environment, line 3435:  Called platform_test 'run' '/build/gru/var/cache/portage/chromeos-base/trunks/out/Default/trunks_testrunner'
trunks-0.0.1-r1535:  *   environment, line 3486:  Called die
trunks-0.0.1-r1535:  * The specific snippet of code:
trunks-0.0.1-r1535:  *       "${cmd[@]}" || die
trunks-0.0.1-r1535:  * 
trunks-0.0.1-r1535:  * If you need support, post the output of `emerge --info '=chromeos-base/trunks-0.0.1-r1535::chromiumos'`,
trunks-0.0.1-r1535:  * the complete build log and the output of `emerge -pqv '=chromeos-base/trunks-0.0.1-r1535::chromiumos'`.
trunks-0.0.1-r1535:  * The complete build log is located at '/build/gru/tmp/portage/logs/chromeos-base:trunks-0.0.1-r1535:20170108-041902.log'.
trunks-0.0.1-r1535:  * For convenience, a symlink to the build log is located at '/build/gru/tmp/portage/chromeos-base/trunks-0.0.1-r1535/temp/build.log'.
trunks-0.0.1-r1535:  * The ebuild environment file is located at '/build/gru/tmp/portage/chromeos-base/trunks-0.0.1-r1535/temp/environment'.
trunks-0.0.1-r1535:  * Working directory: '/build/gru/tmp/portage/chromeos-base/trunks-0.0.1-r1535/work/trunks-0.0.1/aosp/system/tpm/trunks'
trunks-0.0.1-r1535:  * S: '/build/gru/tmp/portage/chromeos-base/trunks-0.0.1-r1535/work/trunks-0.0.1/aosp/system/tpm/trunks'
trunks-0.0.1-r1535: >>> Failed to emerge chromeos-base/trunks-0.0.1-r1535 for /build/gru/, Log file:
trunks-0.0.1-r1535: >>>  '/build/gru/tmp/portage/logs/chromeos-base:trunks-0.0.1-r1535:20170108-041902.log'
trunks-0.0.1-r1535: 
trunks-0.0.1-r1535:  * Messages for package chromeos-base/trunks-0.0.1-r1535 merged to /build/gru/:
trunks-0.0.1-r1535: 
trunks-0.0.1-r1535:  * ERROR: chromeos-base/trunks-0.0.1-r1535::chromiumos failed (test phase):
trunks-0.0.1-r1535:  *   (no error message)
trunks-0.0.1-r1535:  * 
trunks-0.0.1-r1535:  * Call stack:
trunks-0.0.1-r1535:  *     ebuild.sh, line   93:  Called src_test
trunks-0.0.1-r1535:  *   environment, line 3873:  Called platform_src_test
trunks-0.0.1-r1535:  *   environment, line 3453:  Called platform_pkg_test
trunks-0.0.1-r1535:  *   environment, line 3435:  Called platform_test 'run' '/build/gru/var/cache/portage/chromeos-base/trunks/out/Default/trunks_testrunner'
trunks-0.0.1-r1535:  *   environment, line 3486:  Called die
trunks-0.0.1-r1535:  * The specific snippet of code:
trunks-0.0.1-r1535:  *       "${cmd[@]}" || die
trunks-0.0.1-r1535:  * 
trunks-0.0.1-r1535:  * If you need support, post the output of `emerge --info '=chromeos-base/trunks-0.0.1-r1535::chromiumos'`,
trunks-0.0.1-r1535:  * the complete build log and the output of `emerge -pqv '=chromeos-base/trunks-0.0.1-r1535::chromiumos'`.
trunks-0.0.1-r1535:  * The complete build log is located at '/build/gru/tmp/portage/logs/chromeos-base:trunks-0.0.1-r1535:20170108-041902.log'.
trunks-0.0.1-r1535:  * For convenience, a symlink to the build log is located at '/build/gru/tmp/portage/chromeos-base/trunks-0.0.1-r1535/temp/build.log'.
trunks-0.0.1-r1535:  * The ebuild environment file is located at '/build/gru/tmp/portage/chromeos-base/trunks-0.0.1-r1535/temp/environment'.
trunks-0.0.1-r1535:  * Working directory: '/build/gru/tmp/portage/chromeos-base/trunks-0.0.1-r1535/work/trunks-0.0.1/aosp/system/tpm/trunks'
trunks-0.0.1-r1535:  * S: '/build/gru/tmp/portage/chromeos-base/trunks-0.0.1-r1535/work/trunks-0.0.1/aosp/system/tpm/trunks'
=== Complete: job trunks-0.0.1-r1535 (0m6.1s) ===