Fix public deps on generated headers (#4386)

Some generated headers are exposed by headers in the spvtools_opt
target, but its dependency on them is private. This can result in build
flake, since the headers don't need to be generated before compiling
any spvtools_opt dependents.

This fixes the build flake by correctly expressing these as public
dependencies.
diff --git a/BUILD.gn b/BUILD.gn
index fdf4584..32a44ff 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -786,12 +786,14 @@
 
   deps = [
     ":spvtools",
-    ":spvtools_language_header_cldebuginfo100",
     ":spvtools_language_header_debuginfo",
-    ":spvtools_language_header_vkdebuginfo100",
     ":spvtools_vendor_tables_spv-amd-shader-ballot",
   ]
-  public_deps = [ ":spvtools_headers" ]
+  public_deps = [
+    ":spvtools_headers",
+    ":spvtools_language_header_cldebuginfo100",
+    ":spvtools_language_header_vkdebuginfo100",
+  ]
 
   if (build_with_chromium) {
     configs -= [ "//build/config/compiler:chromium_code" ]