ART: Use cerr for host unexpected errors

Use cerr and endl when dumping unexpected signals on Linux. This
simulates the previous special-casing of INTERNAL_FATAL to
immediately print output.

Bug: 31338270
Test: m test-art-host
Test: manual segfault
Change-Id: I9d4471836339bf69681cc4aa43df6d558e7f123d
2 files changed