Docker: Fix Toolchain registration

Toolchains were not registered, as ToolchainBundle(...., AutoRegister)
only registers missing parts of a bundle.

Task-number: QTCREATORBUG-31877
Change-Id: I310b469425ed94274ba12ff5d396b44c9b2eee87
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/docker/kitdetector.cpp

@@ -264,6 +264,7 @@ Toolchains KitDetectorPrivate::autoDetectToolchains()
                                   .arg(toolchain->compilerCommand().toUserOutput()));
             toolchain->setDetectionSource(m_sharedId);
         }
+        ToolchainManager::registerToolchains(newToolchains);
         const QList<ToolchainBundle> bundles
             = ToolchainBundle::collectBundles(newToolchains, ToolchainBundle::AutoRegister::On);
         alreadyKnown.append(newToolchains);