Add -DDAWN_USE_X11=OFF for dawn.node build

Otherwise we gain a default dependency on X11, when on Linux.

Change-Id: Ief52603758f5808a47dde64b04b4f10d27e4c93a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/74880
Auto-Submit: David Neto <dneto@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: David Neto <dneto@google.com>
diff --git a/src/dawn_node/README.md b/src/dawn_node/README.md
index 2faf96c..e967bb0 100644
--- a/src/dawn_node/README.md
+++ b/src/dawn_node/README.md
@@ -30,6 +30,15 @@
 gclient sync
 ```
 
+Optionally, on Linux install X11-xcb support:
+
+```sh
+sudo apt-get install libx11-xcb-dev
+```
+
+If you don't have those supporting libraries, then you must use the
+`-DDAWN_USE_X11=OFF` flag on Cmake.
+
 ### Build
 
 Currently, the node bindings can only be built with CMake:
@@ -37,7 +46,7 @@
 ```sh
 mkdir <build-output-path>
 cd <build-output-path>
-cmake <dawn-root-path> -GNinja -DDAWN_BUILD_NODE_BINDINGS=1 -DDAWN_ENABLE_PIC=1
+cmake <dawn-root-path> -GNinja -DDAWN_BUILD_NODE_BINDINGS=1 -DDAWN_ENABLE_PIC=1 -DDAWN_USE_X11=OFF
 ninja dawn.node
 ```