dri_inteface: add define for checking presence of drm.h

__NOT_HAVE_DRM_H is a like a feature, defined by default on specific platforms
and allows to be defined externally as well.

__NOT_HAVE_DRM_H should only be used by xserver and mesa swrast_dri drivers

include/GL/internal/dri_interface.h

@@ -41,7 +41,13 @@
 #define DRI_INTERFACE_H
 
 /* For archs with no drm.h */
-#if !defined(__APPLE__) && !defined(__CYGWIN__) && !defined(__GNU__)
+#if defined(__APPLE__) || defined(__CYGWIN__) || defined(__GNU__)
+#ifndef __NOT_HAVE_DRM_H
+#define __NOT_HAVE_DRM_H
+#endif
+#endif
+
+#ifndef __NOT_HAVE_DRM_H
 #include <drm.h>
 #else
 typedef unsigned int drm_context_t;

src/mesa/drivers/dri/swrast/Makefile

@@ -5,6 +5,8 @@ include $(TOP)/configs/current
 
 LIBNAME = swrast_dri.so
 
+DRIVER_DEFINES = -D__NOT_HAVE_DRM_H
+
 DRIVER_SOURCES = \
 	swrast.c \
 	swrast_span.c