ARM: change attribute tests to use parsed form

This makes the tests more readable by using the -arm-attributes decoding support
in llvm-readobj since that is now available.  Change the invocation commands to
be similar to other test and use a more precise triple (the tests only require
ARM EABI support).
tools: handle out-of-line personality 0 decoding

In some cases it is possible to have a personality 0 unwinding opcodes in the
extab (such as when .handlerdata is used in the assembly).  Simply decode the 3
opcodes for that case.