Make "Add Qt Sources" work for Qt SDK on Linux (NOT built from source)

This is similar to my question about Step into Qt Sources from Qt Creator on Windows (NOT built from source), but I can't make it work for Linux.

Instead of building from source, I have downloaded the Qt SDK installer, and I've installed Qt to /opt/Qt, and I have the sources at /opt/Qt/5.4/Src.

I cannot step into Qt Sources, so I tried adding a Source Mapping using "Add Qt Sources":

I have tried mapping /var/tmp/qt-src to /opt/Qt/5.4/Src, /opt/Qt/5.4/Src/qtbase, and /opt/Qt/5.4/Src/qtbase/src, none of which worked.

What am I doing wrong? Is the source mapping not /var/tmp/qt-src, or is the target mapping wrong? Does "Add Qt Sources" work at all for the Qt SDK?

I saw a suggestion in a forum thread that it's because the Qt SDK for Linux ships only stripped binaries, while it ships both debug and release DLLs for Windows (which would explain why it worked for Windows, but not for Linux).