Avoid overly large SmallPtrSet/SmallSet

These sets perform linear searching in small mode so it is never a good
idea to use SmallSize/N bigger than 32.

llvm-svn: 259283
diff --git a/llvm/lib/Support/CommandLine.cpp b/llvm/lib/Support/CommandLine.cpp
index fdcdb03..c1615a0 100644
--- a/llvm/lib/Support/CommandLine.cpp
+++ b/llvm/lib/Support/CommandLine.cpp
@@ -1449,7 +1449,7 @@
 static void sortOpts(StringMap<Option *> &OptMap,
                      SmallVectorImpl<std::pair<const char *, Option *>> &Opts,
                      bool ShowHidden) {
-  SmallPtrSet<Option *, 128> OptionSet; // Duplicate option detection.
+  SmallPtrSet<Option *, 32> OptionSet; // Duplicate option detection.
 
   for (StringMap<Option *>::iterator I = OptMap.begin(), E = OptMap.end();
        I != E; ++I) {