A quick fix for benchmark: clean the first removed result, and add "--expunge".

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PiperOrigin-RevId: 150179734
MOS_MIGRATED_REVID=150179734

src/tools/benchmark/java/com/google/devtools/build/benchmark/BazelBuilder.java

diff --git a/src/tools/benchmark/java/com/google/devtools/build/benchmark/BazelBuilder.java b/src/tools/benchmark/java/com/google/devtools/build/benchmark/BazelBuilder.java
index 974ae17..71890b2 100644
--- a/src/tools/benchmark/java/com/google/devtools/build/benchmark/BazelBuilder.java
+++ b/src/tools/benchmark/java/com/google/devtools/build/benchmark/BazelBuilder.java
@@ -119,7 +119,7 @@
 
   @Override
   public void clean() throws CommandException {
-    String[] cleanCommand = {"bazel", "clean"};
+    String[] cleanCommand = {"bazel", "clean", "--expunge"};
     Command cmd = new Command(cleanCommand, null, generatedCodeDir.toFile());
     cmd.execute();
   }

src/tools/benchmark/java/com/google/devtools/build/benchmark/BuildGroupRunner.java

diff --git a/src/tools/benchmark/java/com/google/devtools/build/benchmark/BuildGroupRunner.java b/src/tools/benchmark/java/com/google/devtools/build/benchmark/BuildGroupRunner.java
index aedd764..047a53a 100644
--- a/src/tools/benchmark/java/com/google/devtools/build/benchmark/BuildGroupRunner.java
+++ b/src/tools/benchmark/java/com/google/devtools/build/benchmark/BuildGroupRunner.java
@@ -119,6 +119,7 @@
 
     if (removeFirstResult) {
       buildTargetAndGetElapsedTime(buildBinary, envConfig, targetConfig);
+      builder.clean();
     }
     double elapsedTime = buildTargetAndGetElapsedTime(buildBinary, envConfig, targetConfig);