Provide __main hooks for cygwin & mingw32


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47479 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/System/DynamicLibrary.cpp b/lib/System/DynamicLibrary.cpp
index 44666a3..9c52c8a 100644
--- a/lib/System/DynamicLibrary.cpp
+++ b/lib/System/DynamicLibrary.cpp
@@ -118,6 +118,7 @@
 #ifdef __CYGWIN__
   {
     EXPLICIT_SYMBOL(_alloca);
+    EXPLICIT_SYMBOL(__main);
   }
 #endif