QtSupport: Collect environment changes instead of full environments

Starting creating custom qmakeRunEnvironment() with systemEnvironment
in derived classes without further context breaks down in cases of e.g.
containerized builds.

So instead create the base environment outside where the context is
clear (still wrong after this patch) and let the derived class only
apply the changes they need to an otherwise unspecified environment.

Change-Id: Ibb23844f490ce86d8a89f6ce728faff65865c09b
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/android/androidqtversion.cpp

@@ -145,12 +145,10 @@ void AndroidQtVersion::addToEnvironment(const Kit *k, Utils::Environment &env) c
             config.bestNdkPlatformMatch(qMax(minimumNDK(), AndroidManager::minimumSDK(k)), this));
 }
 
-Utils::Environment AndroidQtVersion::qmakeRunEnvironment() const
+void AndroidQtVersion::setupQmakeRunEnvironment(Utils::Environment &env) const
 {
-    Utils::Environment env = Utils::Environment::systemEnvironment();
     env.set(QLatin1String("ANDROID_NDK_ROOT"),
             AndroidConfigurations::currentConfig().ndkLocation(this).toUserOutput());
-    return env;
 }
 
 QString AndroidQtVersion::description() const