Fix ToolchainResolver to show an error when a toolchain type resolves to an
existing but invalid target.

PiperOrigin-RevId: 241389281
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/AspectFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/AspectFunction.java
index 6ccbdd1..2194808 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/AspectFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/AspectFunction.java
@@ -497,6 +497,10 @@
       }
     } catch (AspectCreationException e) {
       throw new AspectFunctionException(e);
+    } catch (ToolchainException e) {
+      throw new AspectFunctionException(
+          new AspectCreationException(
+              e.getMessage(), new LabelCause(key.getLabel(), e.getMessage())));
     }
   }