Fixes Dawn to use custom Vulkan loader on Linux systems.

- Adds system utility to get the module directory for dawn native.
- Updates Vulkan backend to use the module directory to find loader.
- Test ran on NVIDIA GTX 1660 here: https://chromium-swarm.appspot.com/task?id=576d77991add7c10.

Bug: dawn:1191
Change-Id: I7c577008b5252ac94f38c8cdb56f7e8d8a0aa956
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/70860
Commit-Queue: Loko Kung <lokokung@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

scripts/dawn_features.gni

@@ -15,8 +15,8 @@
 import("//build_overrides/build.gni")
 
 if (build_with_chromium) {
-  import("//build/config/sanitizers/sanitizers.gni")
   import("//build/config/ozone.gni")
+  import("//build/config/sanitizers/sanitizers.gni")
 
   dawn_use_x11 = ozone_platform_x11
 } else {
@@ -97,7 +97,8 @@ declare_args() {
 
   # Uses our built version of the Vulkan loader on platforms where we can't
   # assume to have one present at the system level.
-  dawn_enable_vulkan_loader = dawn_enable_vulkan && is_mac
+  dawn_enable_vulkan_loader =
+      dawn_enable_vulkan && (is_mac || (is_linux && !is_android))
 }
 
 # UWP only supports CoreWindow for windowing

scripts/dawn_overrides_with_defaults.gni

@@ -63,8 +63,7 @@ if (!defined(dawn_swiftshader_dir)) {
 }
 
 if (!defined(dawn_vulkan_loader_dir)) {
-  # Default to the Vulkan loader not being available.
-  dawn_vulkan_loader_dir = ""
+  dawn_vulkan_loader_dir = "//third_party/vulkan-deps/vulkan-loader/src"
 }
 
 if (!defined(dawn_vulkan_validation_layers_dir)) {