Fix ChromeOS compile
Bug: 27177071
TEST=cros_workon_make update_engine builds fine.
Change-Id: Iee571640df5d50a8276ff4cca5dad5961dc238a3
diff --git a/common/platform_constants_chromeos.cc b/common/platform_constants_chromeos.cc
index 7c1d627..3ebcf8a 100644
--- a/common/platform_constants_chromeos.cc
+++ b/common/platform_constants_chromeos.cc
@@ -32,7 +32,7 @@
"/tmp/update-check-response-deadline";
// This directory is wiped during powerwash.
const char kNonVolatileDirectory[] = "/var/lib/update_engine";
-const char kPostinstallMountOptions[] = nullptr;
+const char kPostinstallMountOptions[] = "";
} // namespace constants
} // namespace chromeos_update_engine