Set StageError cause in ChiselStage (#1382)

Signed-off-by: Schuyler Eldridge <[email protected]>

Co-authored-by: Jim Lawson <[email protected]>

src/main/scala/chisel3/stage/ChiselStage.scala

@@ -46,7 +46,7 @@ class ChiselStage extends Stage with PreservesAll[Phase] {
         .augmentString(stackTrace)
         .lines
         .foreach(line => println(s"${ErrorLog.errTag} $line")) // scalastyle:ignore regex
-      throw new StageError()
+      throw new StageError(cause=ce)
   }
 
   /** Convert a Chisel module to a CHIRRTL string