Add validation that all targets used as platforms actually advertise

they provide PlatformInfo.

Fixes #10282.

Closes #10307.

PiperOrigin-RevId: 282766536
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/PlatformLookupUtilTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/PlatformLookupUtilTest.java
index 1ed9020..3e638be 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/PlatformLookupUtilTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/PlatformLookupUtilTest.java
@@ -138,9 +138,9 @@
       return GET_PLATFORM_INFO_FUNCTION;
     }
 
-    abstract Iterable<ConfiguredTargetKey> platformKeys();
+    abstract ImmutableList<ConfiguredTargetKey> platformKeys();
 
-    public static GetPlatformInfoKey create(Iterable<ConfiguredTargetKey> platformKeys) {
+    public static GetPlatformInfoKey create(ImmutableList<ConfiguredTargetKey> platformKeys) {
       return new AutoValue_PlatformLookupUtilTest_GetPlatformInfoKey(platformKeys);
     }
   }
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/SingleToolchainResolutionFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/SingleToolchainResolutionFunctionTest.java
index ee4b18e..f2a5b62 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/SingleToolchainResolutionFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/SingleToolchainResolutionFunctionTest.java
@@ -16,6 +16,7 @@
 
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.devtools.build.skyframe.EvaluationResultSubjectFactory.assertThatEvaluationResult;
+import static org.mockito.Mockito.when;
 
 import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.ImmutableList;
@@ -40,6 +41,7 @@
 import com.google.devtools.build.skyframe.EvaluationResult;
 import com.google.devtools.build.skyframe.SkyKey;
 import javax.annotation.Nullable;
+import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -56,11 +58,12 @@
   @AutoCodec @AutoCodec.VisibleForSerialization
   static final ConfiguredTargetKey MAC_CTKEY = Mockito.mock(ConfiguredTargetKey.class);
 
-  static {
-    Mockito.when(LINUX_CTKEY.functionName())
-        .thenReturn(InjectedActionLookupKey.INJECTED_ACTION_LOOKUP);
-    Mockito.when(MAC_CTKEY.functionName())
-        .thenReturn(InjectedActionLookupKey.INJECTED_ACTION_LOOKUP);
+  @Before
+  public void setUpKeys() {
+    when(LINUX_CTKEY.functionName()).thenReturn(InjectedActionLookupKey.INJECTED_ACTION_LOOKUP);
+    when(LINUX_CTKEY.getLabel()).thenReturn(Label.parseAbsoluteUnchecked("//platforms:linux"));
+    when(MAC_CTKEY.functionName()).thenReturn(InjectedActionLookupKey.INJECTED_ACTION_LOOKUP);
+    when(MAC_CTKEY.getLabel()).thenReturn(Label.parseAbsoluteUnchecked("//platforms:mac"));
   }
 
   private static ConfiguredTargetValue createConfiguredTargetValue(