Build libgltf for Android, too

It won't be used for now, anyway, as libgltf is used only in avmedia and we
don't build any avmedia for Android. But just to make sure the code stays
portable.

Change-Id: I7a4e5ee3d22f28a407d400a65a1704c23dcb1107

configure.ac

@@ -10397,7 +10397,7 @@ dnl ===================================================================
 
 ENABLE_GLTF=
 AC_MSG_CHECKING([whether to enable glTF support])
-if test $_os != iOS -a $_os != Android -a  "x$enable_gltf" != "xno"; then
+if test $_os != iOS -a  "x$enable_gltf" != "xno"; then
     ENABLE_GLTF=TRUE
     AC_MSG_RESULT([yes])
     BUILD_TYPE="$BUILD_TYPE LIBGLTF"