TestHelloWorld uses stack unwinding to get a thread's backtrace.
In case of remote run the test should use system libraries (like libc.so) from a target in order to lookup symbols correctly:
- Added optional environment variable LLDB_IMAGE_SEARCH_PATH that represents root directory for custom search paths.
- lldbtest.addImageSearchPaths registers custom target image search paths for directories that contain at least one file.
In total, the test uses for unwinding a downloaded version of libc.so instead of local one.