Valgrind: Fix error display for shadow build

object() refers to the executable file (the build target), which
doesn't have to be inside the project's directory.

directory() refers to the directory of the frame's source file.

Change-Id: Icf9885d1346acbf42ea904e69d6c8eee4d6a40cb
Reviewed-by: hjk <hjk121@nokiamail.com>