Fix more -Wshorten-64-to-32 warnings.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50659 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/System/Unix/Program.inc b/lib/System/Unix/Program.inc
index 91baefb..d0dade1 100644
--- a/lib/System/Unix/Program.inc
+++ b/lib/System/Unix/Program.inc
@@ -58,7 +58,7 @@
     return Path();
 
   // Now we have a colon separated list of directories to search; try them.
-  unsigned PathLen = strlen(PathStr);
+  size_t PathLen = strlen(PathStr);
   while (PathLen) {
     // Find the first colon...
     const char *Colon = std::find(PathStr, PathStr+PathLen, ':');