1. Read .ARM.exidx and .ARM.extab, provides these data to libunwind
through AccessMem.
2. In FindProcInfo, search .ARM.exidx for the idx entry of function
containing ip.
3. Add structures to store .ARM.exidx info in DebugFrameInfo, and
clean up the structure.
4. Add tests to test each unwind information (.eh_frame, .debug_frame,
.gnu_debugdata, .ARM.exidx) separately.
Bug: http://b/30974693
Test: run backtrace_test.
Test: run simpleperf runtest.py.
Change-Id: I9377a54379158bd35860efcf0e011423be7350d4
Host builds were compiling without -Wl,--no-undefined. Add missing
host ldlibs so that -Wl,--no-undefined can be added again.
Test: m -j host
Bug: 32305815
Change-Id: I0ceabc3f4ec74e2f737afaac58810c5d53d6ccb6
