build error on PPC in imageFormatForMasks

/home/rutledge/dev/qt511/qtbase/src/plugins/platforms/xcb/qxcbimage.cpp: In function ‘QImage::Format {anonymous}::imageFormatForMasks(int, int, int, int)’:
/home/rutledge/dev/qt511/qtbase/src/plugins/platforms/xcb/qxcbimage.cpp:72:26: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
             if (red_mask == 0xff000000 && blue_mask == 0xff00)
                          ^
/home/rutledge/dev/qt511/qtbase/src/plugins/platforms/xcb/qxcbimage.cpp:93:26: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
             if (red_mask == 0xff000000 && blue_mask == 0xff00)
                          ^

06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  68) #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  69)             if (red_mask == 0xff && blue_mask == 0xff0000)
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  70)                 return QImage::Format_RGBA8888_Premultiplied;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  71) #else
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  72)             if (red_mask == 0xff000000 && blue_mask == 0xff00)
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  73)                 return QImage::Format_RGBA8888_Premultiplied;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  74) #endif
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  75)             if (red_mask == 0x3ff && blue_mask == 0x3ff00000)
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  76)                 return QImage::Format_A2BGR30_Premultiplied;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  77)             if (red_mask == 0x3ff00000 && blue_mask == 0x3ff)
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  78)                 return QImage::Format_A2RGB30_Premultiplied;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  79)             break;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  80)         case 30:
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  81)             if (red_mask == 0x3ff && blue_mask == 0x3ff00000)
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  82)                 return QImage::Format_BGR30;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  83)             if (blue_mask == 0x3ff && red_mask == 0x3ff00000)
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  84)                 return QImage::Format_RGB30;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  85)             break;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  86)         case 24:
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  87)             if (red_mask == 0xff0000 && blue_mask == 0xff)
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  88)                 return QImage::Format_RGB32;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  89) #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  90)             if (red_mask == 0xff && blue_mask == 0xff0000)
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  91)                 return QImage::Format_RGBX8888;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  92) #else
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  93)             if (red_mask == 0xff000000 && blue_mask == 0xff00)
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  94)                 return QImage::Format_RGBX8888;
06089a19 (Allan Sandfeld Jensen 2017-09-28 14:10:10 +0200  95) #endif