Update "--subcommands" to also show the execution platform for each action.

PiperOrigin-RevId: 314537921

src/main/java/com/google/devtools/build/lib/actions/ActionExecutionContext.java

diff --git a/src/main/java/com/google/devtools/build/lib/actions/ActionExecutionContext.java b/src/main/java/com/google/devtools/build/lib/actions/ActionExecutionContext.java
index d98bb54..d47fb64 100644
--- a/src/main/java/com/google/devtools/build/lib/actions/ActionExecutionContext.java
+++ b/src/main/java/com/google/devtools/build/lib/actions/ActionExecutionContext.java
@@ -293,18 +293,21 @@
       return;
     }
 
-    String reason;
+    StringBuilder reason = new StringBuilder();
     ActionOwner owner = spawn.getResourceOwner().getOwner();
     if (owner == null) {
-      reason = spawn.getResourceOwner().prettyPrint();
+      reason.append(spawn.getResourceOwner().prettyPrint());
     } else {
-      reason =
-          Label.print(owner.getLabel())
-              + " ["
-              + spawn.getResourceOwner().prettyPrint()
-              + ", configuration: "
-              + owner.getConfigurationChecksum()
-              + "]";
+      reason.append(Label.print(owner.getLabel()));
+      reason.append(" [");
+      reason.append(spawn.getResourceOwner().prettyPrint());
+      reason.append(", configuration: ");
+      reason.append(owner.getConfigurationChecksum());
+      if (owner.getExecutionPlatform() != null) {
+        reason.append(", execution platform: ");
+        reason.append(owner.getExecutionPlatform().label());
+      }
+      reason.append("]");
     }
     String message = Spawns.asShellCommand(spawn, getExecRoot(), showSubcommands.prettyPrintArgs);
     getEventHandler().handle(Event.of(EventKind.SUBCOMMAND, null, "# " + reason + "\n" + message));