CMake: Disable Tint's GLSL writer

Currently enabling this build target requires a dependency on glslang, which Dawn does not provide.
Just disable this target while we figure how we want to tackle this.

Bug: tint:1217
Change-Id: I79f2ef6e1b007e69ad4aa0d40500b0d1c6a52d6f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/66605
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Stephen White <senorblanco@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>
diff --git a/third_party/CMakeLists.txt b/third_party/CMakeLists.txt
index d78c72e..e3201fa 100644
--- a/third_party/CMakeLists.txt
+++ b/third_party/CMakeLists.txt
@@ -59,6 +59,10 @@
 
 if (NOT TARGET libtint)
     message(STATUS "Dawn: using Tint at ${DAWN_TINT_DIR}")
+    # TODO(crbug.com/tint/1217): Tint expects glslang for validation when
+    # building the GLSL writer, but currently Dawn does not provide this
+    # third_party dependency. Disable the GLSL writer for now.
+    set(TINT_BUILD_GLSL_WRITER OFF)
     add_subdirectory(${DAWN_TINT_DIR} "${CMAKE_CURRENT_BINARY_DIR}/tint")
 endif()