title: How to install and debug older Qt versions in newer Qt and QtCreator?
body: <p>When I updated from Qt 5.6 to 5.12, I had to revert one of the projects that I was working to Qt 5.6, and turned out that the two Qt installations where messing with each other. Unfortunately, Qt 5.12 installer does not provide an option to install 5.6 anymore.</p>
  <p>So I decided to move the Qt 5.6 SDK to inside the Qt folder with the 5.12 installation. After setting up QtCreator to use both versions, everything worked fine, except I could not debug the 5.6 version anymore. It gave me an error in the path to Qt 5.6 lib folder (it was pointing to the old directory) when linking, and another one in the debug log:</p>
  <pre><code>This application failed to start because it could not find or load the Qt platform plugin &quot;cocoa&quot; in &quot;&quot;
  </code></pre>
  <p>After searching for all files in qt installation folder using the old path, I replaced all occurrences with the new path but the issue persisted. It was when I realized that the previous path was also hardcoded in some binary files that qt uses like QtCore_debug. I searched on the internet for ways to regenerate these files but I could not find anything.</p>