Relax assertion in CFG builder when processing ForStmts.  This fixes an assertion failure
on code containing GNU statement expressions reported in PR 8141.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@113953 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CFG.cpp b/lib/Analysis/CFG.cpp
index e297ec4..cc3a388 100644
--- a/lib/Analysis/CFG.cpp
+++ b/lib/Analysis/CFG.cpp
@@ -991,7 +991,8 @@
   if (Stmt* C = F->getCond()) {
     Block = ExitConditionBlock;
     EntryConditionBlock = addStmt(C);
-    assert(Block == EntryConditionBlock);
+    assert(Block == EntryConditionBlock ||
+           (Block == 0 && EntryConditionBlock == Succ));
 
     // If this block contains a condition variable, add both the condition
     // variable and initializer to the CFG.