base: Add TemporaryFile::DoNotRemove().

Bug: http://b/73127105
Test: none.
Change-Id: I563c12bfb629ddd630568dda4817fb10cc9940a8
diff --git a/base/test_utils.cpp b/base/test_utils.cpp
index 9d8dfb2..1619c21 100644
--- a/base/test_utils.cpp
+++ b/base/test_utils.cpp
@@ -92,7 +92,9 @@
   if (fd != -1) {
     close(fd);
   }
-  unlink(path);
+  if (remove_file_) {
+    unlink(path);
+  }
 }
 
 int TemporaryFile::release() {