Kit: Improve toolchain setup on auto-detected kit setup

The auto-detected Kit used by default in creator used to set up a
set of toolchains, that usually match up with each other (this relies
on the auto-detecion of toolchains to detect groups of compilers
in one go).

Then the Qt version selected (or better: The mkspec) will change the
C++ compiler if necessary.

Change this to actually pick a good C++ compiler and also update all
other toolchains to match the C++ compiler.

Task-number: QTCREATORBUG-18571
Change-Id: I95ddd9b83cf1642fba648919b76d3e3b7aa24c43
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/qmakeprojectmanager/qmakekitinformation.cpp

@@ -95,7 +95,7 @@ void QmakeKitInformation::setup(Kit *k)
                     = Utils::findOr(possibleTcs, possibleTcs.last(),
                                     [&spec](const ToolChain *t) { return t->suggestedMkspecList().contains(spec); });
             if (possibleTc)
-                ToolChainKitInformation::setToolChain(k, possibleTc);
+                ToolChainKitInformation::setAllToolChainsToMatch(k, possibleTc);
         }
     }
 }