[tools][tests] Fix defaultTintPath() for windows

It was not including the '.exe' extension

Change-Id: I589b7a09269228e99e00d2102e252024f7b866a4
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/175223
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: Ben Clayton <bclayton@google.com>
diff --git a/tools/src/cmd/tests/main.go b/tools/src/cmd/tests/main.go
index a2405cd..4a3cfaf 100644
--- a/tools/src/cmd/tests/main.go
+++ b/tools/src/cmd/tests/main.go
@@ -1112,12 +1112,7 @@
 	}
 }
 
-// defaultRootPath returns the default path to the root of the test tree
-func defaultRootPath() string {
-	return filepath.Join(fileutils.DawnRoot(), "test/tint")
-}
-
 // defaultTintPath returns the default path to the tint executable
 func defaultTintPath() string {
-	return filepath.Join(fileutils.DawnRoot(), "out/active/tint")
+	return filepath.Join(fileutils.DawnRoot(), "out", "active", "tint"+fileutils.ExeExt)
 }