configure: Require libudev for drm & wayland egl platforms

NOTE: This is a candidate for the 7.11 branch.
diff --git a/configure.ac b/configure.ac
index 74a511e..7d0f3d8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1724,6 +1724,10 @@
         if test "$plat" = "drm" && test "x$enable_gbm" = "xno"; then
                 AC_MSG_ERROR([EGL platform drm needs gbm])
         fi
+        case "$plat$have_libudev" in
+                waylandno|drmno)
+                    AC_MSG_ERROR([cannot build $plat platfrom without udev]) ;;
+        esac
     done
     EGL_PLATFORMS="$egl_platforms"
     ;;