GlobalISel: don't leak super-entry BB when merging with IR-level one.

We have to delete the block manually or it leaks. That triggers failures in
-fsanitize=leak bots (unsurprisingly), which should be fixed by this patch.

llvm-svn: 293347
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 9382de7..1a667d6 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -965,6 +965,7 @@
     // Get rid of the now empty basic block.
     EntryBB->removeSuccessor(&NewEntryBB);
     MF->remove(EntryBB);
+    MF->DeleteMachineBasicBlock(EntryBB);
 
     assert(&MF->front() == &NewEntryBB &&
            "New entry wasn't next in the list of basic block!");