Fix potential buffer overflow


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46296 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/System/Win32/Program.inc b/lib/System/Win32/Program.inc
index 3badb19..cb00213 100644
--- a/lib/System/Win32/Program.inc
+++ b/lib/System/Win32/Program.inc
@@ -134,7 +134,7 @@
   }
 
   // Now build the command line.
-  char *command = reinterpret_cast<char *>(_alloca(len));
+  char *command = reinterpret_cast<char *>(_alloca(len+1));
   char *p = command;
 
   for (unsigned i = 0; args[i]; i++) {