Make Mock ICD json file a data_dep of Mock ICD

Bug: angleproject:2471

Mock ICD json file was only being copied to angledata when "build all"
was done. This fix causes the json file to be copied anytime something
with a Vulkan dep is compiled.

Change-Id: Ic56ecf12ff5996d14bd2ed419f50b2362453b939
Reviewed-on: https://chromium-review.googlesource.com/1020233
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>

third_party/vulkan-validation-layers/BUILD.gn

@@ -525,6 +525,9 @@ if (!is_android) {
       "//build/config:exe_and_shlib_deps",
     ]
     deps += [ ":vulkan_generate_mock_icd_files" ]
+    data_deps = [
+      ":vulkan_gen_icd_json_file",
+    ]
     sources = mock_icd_sources
     if (is_win) {
       sources += [ "src/icd/VkICD_mock_icd.def" ]