trim whitespace from windows error messages

the messages contain a trailing CRLF, which is not helpful.

Change-Id: I4a27115a191dc416a62e28a41f2a9c5893bdc64b
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

qmake/library/qmakebuiltins.cpp

@@ -214,7 +214,7 @@ static QString windowsErrorCode()
                   NULL);
     QString ret = QString::fromWCharArray(string);
     LocalFree((HLOCAL)string);
-    return ret;
+    return ret.trimmed();
 }
 #endif