With previous changes, I am able to run backtrace_test with
shared library build of libc++abi and libunwind.
I believe we can enable this test for ARM now!
(p.s. This is the 6/6 patch to fix the backtrace_test and libgcc support.)
Hurray! When all the other patches are merged, this is obviously approved! :)
Thanks. Committed as rL226823.