Building xf86-ati:

../../src/drmmode_display.c: In function 'drmmode_set_scanout_pixmap':
../../src/drmmode_display.c:975:2: error: too few arguments to function 'PixmapStartDirtyTracking'
  PixmapStartDirtyTracking(ppix, screenpix, 0, 0);
  ^
In file included from /usr/include/xorg/gc.h:54:0,
                 from /usr/include/xorg/dix.h:51,
                 from /usr/include/xorg/privates.h:151,
                 from /usr/include/xorg/cursor.h:53,
                 from /usr/include/xorg/cursorstr.h:50,
                 from ../../src/drmmode_display.c:35:
/usr/include/xorg/pixmap.h:120:1: note: declared here
 PixmapStartDirtyTracking(PixmapPtr src,
 ^

and 

../../src/radeon_kms.c: In function 'redisplay_dirty':
../../src/radeon_kms.c:290:2: error: too many arguments to function 'PixmapSyncDirtyHelper'
  PixmapSyncDirtyHelper(dirty, &pixregion);
  ^
In file included from /usr/include/xorg/gc.h:54:0,
                 from /usr/include/xorg/dix.h:51,
                 from /usr/include/xorg/privates.h:151,
                 from /usr/include/xorg/cursor.h:53,
                 from /usr/include/xorg/scrnintstr.h:53,
                 from /usr/include/xorg/xf86str.h:39,
                 from ../../src/radeon.h:46,
                 from ../../src/radeon_kms.c:34:
/usr/include/xorg/pixmap.h:131:1: note: declared here
 PixmapSyncDirtyHelper(PixmapDirtyUpdatePtr dirty);
 ^

See full log at http://build.gnome.org/continuous/buildmaster/builds/2015/07/09/8/build/log-xorg-driver-xf86-video-ati.txt