CPack: Use real path to PackageMaker to find its version file (#12621)

On machines where a usr/bin/packagemaker symlink is found, we were
unable to find the version.plist file relative to the symlink.
Resolve the symlink first, so we can find it relative to the
real PackageMaker.

Source/CPack/cmCPackPackageMakerGenerator.cxx

@@ -402,6 +402,9 @@ int cmCPackPackageMakerGenerator::InitializeInternal()
     this->SetOptionIfNotSet("CPACK_INSTALLER_PROGRAM", pkgPath.c_str());
     }
 
+  // Get path to the real PackageMaker, not a symlink:
+  pkgPath = cmSystemTools::GetRealPath(pkgPath.c_str());
+  // Up from there to find the version.plist file in the "Contents" dir:
   std::string contents_dir;
   contents_dir = cmSystemTools::GetFilenamePath(pkgPath);
   contents_dir = cmSystemTools::GetFilenamePath(contents_dir);