Fixed QOpenGLShader::log().

log() returned an empty string because the compile log was stored
in a local variable rather than the member variable.

Change-Id: I60142fd0bccfcbb495cea430b583f81fb0241329
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

src/gui/opengl/qopenglshaderprogram.cpp

@@ -265,7 +265,6 @@ bool QOpenGLShaderPrivate::compile(QOpenGLShader *q)
             glfuncs->glGetShaderSource(shader, sourceCodeLength, &temp, sourceCodeBuffer);
         }
 
-        QString log;
         if (logBuffer)
             log = QString::fromLatin1(logBuffer);
         else