gh-144492: Fix process_changed_files outputs for reusable-{macos, wasi}.yml (GH-144518)

Fix `process_changed_files` double-processing reusable-{macos, wasi] ending up with incorrect outputs
(cherry picked from commit fd190d1)

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

Author: StanFromIreland

Tools/build/compute-changes.py

@@ -227,9 +227,12 @@ def process_changed_files(changed_files: Set[Path]) -> Outputs:
             if file.name == "reusable-windows-msi.yml":
                 run_windows_msi = True
             if file.name == "reusable-macos.yml":
+                run_tests = True
                 platforms_changed.add("macos")
             if file.name == "reusable-wasi.yml":
+                run_tests = True
                 platforms_changed.add("wasi")
+            continue
 
         if not doc_file and file not in RUN_TESTS_IGNORE:
             run_tests = True