display-hal: Exclude HWC libs compilation.

This change introduces compilation flag to
compile standalone SDM libs.

Change-Id: I3f8cde50e1806c6cf157364657d77fd9a780d5e3

libgralloc/framebuffer.cpp

@@ -34,7 +34,9 @@
 #include <linux/fb.h>
 #include <linux/msm_mdp.h>
 
+#ifndef TARGET_HEADLESS
 #include <GLES/gl.h>
+#endif
 
 #include "gralloc_priv.h"
 #include "fb_priv.h"
@@ -99,7 +101,9 @@ static int fb_compositionComplete(struct framebuffer_device_t* dev)
     if(!dev) {
         return -1;
     }
+#ifndef TARGET_HEADLESS
     glFinish();
+#endif
 
     return 0;
 }