Fix name of libdawn_webgpu_dawn to libwebgpu_dawn

Fixed: dawn:1298
Change-Id: I7a32b644349837fcfc5e258232285b591f7e99a8
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/129860
Commit-Queue: Austin Eng <enga@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/dawn/native/BUILD.gn

@@ -883,6 +883,7 @@ dawn_component("webgpu_dawn") {
   #    - SwiftShader can't be built without use_custom_libcxx.
   #      It should be built separately.
   DEFINE_PREFIX = "WGPU"
+  output_name = "webgpu_dawn"
 
   sources = get_target_outputs(":webgpu_dawn_native_proc_gen")
   deps = [