Refactor error reporting in `OatFileBase::Setup()`.

Add a helper function adding a common prefix to the error
messages where we previously had a few different prefixes.
The refactoring slightly reduces the length of the main
`OatFileBase::Setup()` function which is very close to the
500 non-comment code lines limit enforced by `cpplint`.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 38313278
Change-Id: I1dc71342270dee8548e0cca292b86aac7463daf7
1 file changed