Fix standalone emulator build.

- Allow building with OpenGL ES acceleration disabled, avoiding a
  dependency on stuff outside the QEMU project.
- Allow the standalone configure.sh to provide the include/lib path
  for the OpenGL ES libraries.
- Update the default OpenGL ES include path for standalone builds.

Change-Id: I03f4627af4c271783b65a116ceb5934385c68cdc
diff --git a/Makefile.android b/Makefile.android
index 7b35039..7e66bd9 100644
--- a/Makefile.android
+++ b/Makefile.android
@@ -116,6 +116,9 @@
     endif
     ccache :=
   endif
+
+  QEMU_OPENGLES_INCLUDE := sdk/emulator/opengl/host/include
+  QEMU_OPENGLES_LIBS := $(HOST_OUT)
 endif