rust: De-duplicate depLinkFlags

In some cases, duplicate link flags can bubble up through dependencies,
which may cause link-time errors if e.g. they involve whole-static
libraries. Deduplicate these to avoid this issue.

Bug: 391296959
Test: m rust
Change-Id: I1b14a847cf57d588a28a52cdcefeca443d4d56ac
diff --git a/rust/rust.go b/rust/rust.go
index ba6e293..861090b 100644
--- a/rust/rust.go
+++ b/rust/rust.go
@@ -1635,6 +1635,7 @@
 	depPaths.depClangFlags = android.FirstUniqueStrings(depPaths.depClangFlags)
 	depPaths.depIncludePaths = android.FirstUniquePaths(depPaths.depIncludePaths)
 	depPaths.depSystemIncludePaths = android.FirstUniquePaths(depPaths.depSystemIncludePaths)
+	depPaths.depLinkFlags = android.FirstUniqueStrings(depPaths.depLinkFlags)
 
 	return depPaths
 }