Fixed few warnings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160142 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/Unix/Path.inc b/lib/Support/Unix/Path.inc
index ddc1e0f..b41390a 100644
--- a/lib/Support/Unix/Path.inc
+++ b/lib/Support/Unix/Path.inc
@@ -884,7 +884,8 @@
 }
 
 void Path::UnMapFilePages(const char *BasePtr, size_t FileSize) {
-  ::munmap((void*)BasePtr, FileSize);
+  const void *Addr = static_cast<const void *>(BasePtr);
+  ::munmap(const_cast<void *>(Addr), FileSize);
 }
 
 } // end llvm namespace