IOutputParser: Make sure to not cut too much output

Introduce a method to cut away whitespaces from the end of a string
and use it consistently. This avoids a chain of parsers to repeatedly
cut away the last character, assuming that will be the line-break.

Task-number: QTCREATORBUG-9032
Change-Id: I68261c10873535faf94c885c914cd00510ed75d8
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/qt4projectmanager/qmakeparser.cpp

@@ -44,7 +44,7 @@ QMakeParser::QMakeParser() : m_error(QLatin1String("^(.+):(\\d+):\\s(.+)$"))
 
 void QMakeParser::stdError(const QString &line)
 {
-    QString lne(line.trimmed());
+    QString lne = rightTrimmed(line);
     if (lne.startsWith(QLatin1String("Project ERROR:"))) {
         const QString description = lne.mid(15);
         emit addTask(Task(Task::Error,