Use String8/16 c_str [tools]

Bug: 295394788
Test: make checkbuild
Change-Id: I82d6899d8c15a10b15399c39177290012bb5f13b
diff --git a/libs/androidfw/ConfigDescription.cpp b/libs/androidfw/ConfigDescription.cpp
index cf2fd6f..e08030c 100644
--- a/libs/androidfw/ConfigDescription.cpp
+++ b/libs/androidfw/ConfigDescription.cpp
@@ -905,7 +905,7 @@
 
 std::string ConfigDescription::to_string() const {
   const String8 str = toString();
-  return std::string(str.string(), str.size());
+  return std::string(str.c_str(), str.size());
 }
 
 bool ConfigDescription::Dominates(const ConfigDescription& o) const {