Utils: Replace Environment.isValid() with .hasChanges()

That's closer to the intended semantics. The "other" use in docker
will be changed to an optional<Environment> as follow-up to
keep this here mechanical.

Change-Id: I43ef9da6c9c7731b28f9d6fab6413ce9c4f428b4
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/android/androidrunnerworker.cpp

@@ -605,7 +605,7 @@ void AndroidRunnerWorker::asyncStartHelper()
              << QString::fromLatin1(appArgs.join(' ').toUtf8().toBase64());
     }
 
-    if (m_extraEnvVars.isValid()) {
+    if (m_extraEnvVars.hasChanges()) {
         args << "-e" << "extraenvvars"
              << QString::fromLatin1(m_extraEnvVars.toStringList().join('\t')
                                     .toUtf8().toBase64());