Normalize map-like settings in CoreOptions

Keeps the analysis cache around if e.g. `--test_env=foo=baz` changes to `--test_env=foo=bar --test_env=foo=baz`.

Fixes #6667

Closes #18306.

PiperOrigin-RevId: 530192685
Change-Id: I2c2ee95be6635220c847eeee1e9df4baabe5e3af

src/main/java/com/google/devtools/build/lib/analysis/config/CoreOptions.java

@@ -1050,6 +1050,19 @@ public LinkedHashMap<String, String> getNormalizedCommandLineBuildVariables() {
     return flagValueByName;
   }
 
+  // Normalizes list of map entries by keeping only the last entry for each key.
+  private static List<Map.Entry<String, String>> normalizeEntries(
+      List<Map.Entry<String, String>> entries) {
+    LinkedHashMap<String, String> normalizedEntries = new LinkedHashMap<>();
+    for (Map.Entry<String, String> entry : entries) {
+      normalizedEntries.put(entry.getKey(), entry.getValue());
+    }
+    if (normalizedEntries.size() == entries.size()) {
+      return entries;
+    }
+    return normalizedEntries.entrySet().stream().map(SimpleEntry::new).collect(toImmutableList());
+  }
+
   /// Normalizes --features flags by sorting the values and having disables win over enables.
   private static List<String> getNormalizedFeatures(List<String> features) {
     // Parse out the features into a Map<String, boolean>, where the boolean represents whether
@@ -1104,6 +1117,11 @@ public CoreOptions getNormalized() {
     // Normalize features.
     result.defaultFeatures = getNormalizedFeatures(defaultFeatures);
 
+    result.actionEnvironment = normalizeEntries(actionEnvironment);
+    result.hostActionEnvironment = normalizeEntries(hostActionEnvironment);
+    result.testEnvironment = normalizeEntries(testEnvironment);
+    result.commandLineFlagAliases = normalizeEntries(commandLineFlagAliases);
+
     return result;
   }
 }