Don't double-initialize cl::opt for iterating in reverse order to uncover non-determinism in codegen by default

Bots are broken and needs to be fixed before having this on by default.
The feature was committed in r289619.

I tried to disable it in r289624 and failed because it was initialized in two places.

llvm-svn: 289626
diff --git a/llvm/lib/Support/CommandLine.cpp b/llvm/lib/Support/CommandLine.cpp
index f4d501a..fa1782c 100644
--- a/llvm/lib/Support/CommandLine.cpp
+++ b/llvm/lib/Support/CommandLine.cpp
@@ -52,7 +52,7 @@
 // This will help uncover differences in codegen caused due to undefined
 // iteration order.
 static cl::opt<bool, true> ReverseIteration("reverse-iterate",
-  cl::location(ReverseIterate<bool>::value), cl::init(true));
+  cl::location(ReverseIterate<bool>::value));
 }
 #endif