Implement __gnu_Unwind_Find_exidx/__cxa_type_match

Leaving these unimplemented causes linker to have 2 weak undefined
symbols which in turn results in 3 unwanted relocations for arm arch.
Implementing them removes unwanted relocations from resulted dynamic
object

Test: make && readelf --dyn-sym linker
Test: linker-unit-tests && bionic-unit-tests --gtest_filter=dl*:Dl*
Test: flash and boot angler
Change-Id: I10120271936c770659239898aaf852d31c5483c2