[turbofan] Turn a never executing condition into a CHECK

Graph creation used to handle exception throwing gracefully, but this
seems to never happen, so turned it into a CHECK instead.

Change-Id: I90f8471fe77eb66402fd8abe0d5b15dcffee49bf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1784286
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63552}

src/compiler/pipeline.cc

@@ -1000,7 +1000,7 @@ PipelineCompilationJob::Status PipelineCompilationJob::PrepareJobImpl(
   Deoptimizer::EnsureCodeForDeoptimizationEntries(isolate);
 
   if (!pipeline_.CreateGraph()) {
-    if (isolate->has_pending_exception()) return FAILED;  // Stack overflowed.
+    CHECK(!isolate->has_pending_exception());
     return AbortOptimization(BailoutReason::kGraphBuildingFailed);
   }