debuggerd: report crashes even when out of file descriptors.

Use nasty clone hacks to let us close random file descriptors to be
able to connect to debuggerd when the fd table is full.

Bug: http://b/32013594
Test: crasher exhaustfd-SIGSEGV
Change-Id: I47772e9a5994da4473bd935b105d9c36827c017a
4 files changed