compiler: Ensure that Panic.Plain.assertPanic' provides callstack

In 36cddd2c @alt-romes removed CallStack
output from `GHC.Utils.Panic.Plain.assertPanic'`. While this output is
redundant due to the exception backtrace proposal, we may be
bootstrapping with a compiler which does not yet include this machinery.
Reintroduce the output for now.

Fixes #25898.

compiler/GHC/Utils/Panic/Plain.hs

@@ -116,9 +116,17 @@ assertPanic file line =
   Exception.throw (Exception.AssertionFailed
            ("ASSERT failed! file " ++ file ++ ", line " ++ show line))
 
-
+-- | Throw a failed assertion exception taking the location information
+-- from 'HasCallStack' evidence.
 assertPanic' :: HasCallStack => a
-assertPanic' = Exception.throw (Exception.AssertionFailed "ASSERT failed!")
+assertPanic' =
+    Exception.throw
+      $ Exception.AssertionFailed
+      $ "ASSERT failed!\n" ++ withFrozenCallStack doc
+  where
+    -- TODO: Drop CallStack when exception backtrace functionality
+    -- can be assumed of bootstrap compiler.
+    doc = unlines $ fmap ("  "++) $ lines (prettyCallStack callStack)
 
 assert :: HasCallStack => Bool -> a -> a
 {-# INLINE assert #-}