Roll shaderc and glslang and use their BUILD.gn

This rolls glslang and shaderc to be able to use their BUILD.gn files,
and also rolls SPIRV-Tools and spirv-headers to have compatible
versions.

BUG=chromium:870747

Change-Id: I13c615f6f3d148c9b69f06547992bf5910e04e62
Reviewed-on: https://dawn-review.googlesource.com/c/1680
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
diff --git a/scripts/dawn_overrides_with_defaults.gni b/scripts/dawn_overrides_with_defaults.gni
index 5ac07c0..7c47e02 100644
--- a/scripts/dawn_overrides_with_defaults.gni
+++ b/scripts/dawn_overrides_with_defaults.gni
@@ -24,30 +24,26 @@
   dawn_standalone = false
 }
 
-if (!defined(dawn_spirv_cross_dir)) {
-  dawn_spirv_cross_dir = "//third_party/spirv-cross"
-}
-
-if (!defined(dawn_googletest_dir)) {
-  dawn_googletest_dir = "//third_party/googletest"
-}
-
-if (!defined(dawn_glslang_dir)) {
-  dawn_glslang_dir = "//third_party/glslang"
-}
-
-if (!defined(dawn_spirv_tools_dir)) {
-  dawn_spirv_tools_dir = "//third_party/SPIRV-Tools"
-}
-
-if (!defined(dawn_shaderc_dir)) {
-  dawn_shaderc_dir = "//third_party/shaderc"
+if (!defined(dawn_jinja2_dir)) {
+  dawn_jinja2_dir = "//third_party/jinja2"
 }
 
 if (!defined(dawn_glfw_dir)) {
   dawn_glfw_dir = "//third_party/glfw"
 }
 
-if (!defined(dawn_jinja2_dir)) {
-  dawn_jinja2_dir = "//third_party/jinja2"
+if (!defined(dawn_googletest_dir)) {
+  dawn_googletest_dir = "//third_party/googletest"
+}
+
+if (!defined(dawn_shaderc_dir)) {
+  dawn_shaderc_dir = "//third_party/shaderc"
+}
+
+if (!defined(dawn_spirv_cross_dir)) {
+  dawn_spirv_cross_dir = "//third_party/spirv-cross"
+}
+
+if (!defined(dawn_spirv_tools_dir)) {
+  dawn_spirv_tools_dir = "//third_party/SPIRV-Tools"
 }