Debugging helpers: Fix building

- Report errors correctly.
- Do not pass empty target argument to qmake
- Give 'make' a longer timeout and change timeout checking to
  trigger after last output line was obtained from process
- Make build log dialog non-modal and ensure it pops up on failure
  even if a different Qt version was selected in-between
- Disable Rebuild-button while build is running.

Reviewed-by: Kai Köhne <kai.koehne@nokia.com>
Reviewed-by: Lasse Holmstedt <lasse.holmstedt@nokia.com>

src/plugins/projectexplorer/debugginghelper.cpp

@@ -116,11 +116,12 @@ QString DebuggingHelperLibrary::copy(const QString &qtInstallData,
     return QString();
 }
 
-QString DebuggingHelperLibrary::build(const QString &directory, const QString &makeCommand,
+bool DebuggingHelperLibrary::build(const QString &directory, const QString &makeCommand,
                                       const QString &qmakeCommand, const QString &mkspec,
-                                      const Utils::Environment &env, const QString &targetMode)
+                                      const Utils::Environment &env, const QString &targetMode,
+                                      QString *output, QString *errorMessage)
 {
     return buildHelper(QCoreApplication::translate("ProjectExplorer::DebuggingHelperLibrary",
                                                    "GDB helper"), QLatin1String("gdbmacros.pro"), directory,
-                       makeCommand, qmakeCommand, mkspec, env, targetMode);
+                       makeCommand, qmakeCommand, mkspec, env, targetMode, output, errorMessage);
 }