Mask out EXC_SYSCALL exceptions as well. <rdar://problem/31335814>
Mask out EXC_SYSCALL exceptions as well.
<rdar://problem/31335814>

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@299040 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 6c032fa43e5af6d25c1cebbc480c1571ebd2b466)
(cherry picked from commit e46adb96d75441d22eb0430f995b02c1cd4e3a33)

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb