Detect Qt5 in PATH

QMake is of version 3.0 in Qt5 and we failed to get the Qt version
from its output due to this.

Change-Id: I3208868d4cde652a3dd1e45f78d4f349b0acdd37
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

src/libs/utils/buildablehelperlibrary.cpp

@@ -108,7 +108,9 @@ QString BuildableHelperLibrary::qtVersionForQMake(const QString &qmakePath, bool
     static QRegExp regexp(QLatin1String("(QMake version|QMake version:)[\\s]*([\\d.]*)"),
                           Qt::CaseInsensitive);
     regexp.indexIn(output);
-    if (regexp.cap(2).startsWith(QLatin1String("2."))) {
+    const QString qmakeVersion = regexp.cap(2);
+    if (qmakeVersion.startsWith(QLatin1String("2."))
+            || qmakeVersion.startsWith(QLatin1String("3."))) {
         static QRegExp regexp2(QLatin1String("Using Qt version[\\s]*([\\d\\.]*)"),
                                Qt::CaseInsensitive);
         regexp2.indexIn(output);