ninja: Dedupe Swift link args of external deps

To avoid warnings about duplicate “-l” flags.

mesonbuild/backend/ninjabackend.py

@@ -2143,7 +2143,17 @@ def determine_swift_external_dep_link_args(self, target, swiftc):
             if isinstance(d, build.StaticLibrary):
                 for dep in d.get_external_deps():
                     args += swiftc.get_dependency_link_args(dep)
-        return args
+
+        deduped_args = []
+        seen_libs = set()
+        for arg in args:
+            if arg.startswith("-l"):
+                if arg not in seen_libs:
+                    deduped_args.append(arg)
+                    seen_libs.add(arg)
+            else:
+                deduped_args.append(arg)
+        return deduped_args
 
     def get_swift_link_deps(self, target):
         result = []