Remove an extra map lookup from SpawnInputExpander.

Closes #8595.

PiperOrigin-RevId: 253566542
diff --git a/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java b/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java
index 5f0cc2f..6285f31 100644
--- a/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java
+++ b/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java
@@ -97,9 +97,7 @@
       PathFragment targetLocation,
       ActionInput input) {
     Preconditions.checkArgument(!targetLocation.isAbsolute(), targetLocation);
-    if (!inputMappings.containsKey(targetLocation)) {
-      inputMappings.put(targetLocation, input);
-    }
+    inputMappings.put(targetLocation, input);
   }
 
   /** Adds runfiles inputs from runfilesSupplier to inputMappings. */