Revert "Revert "Don't show HIDL_GENERATED_ with -Lc++-impl.""

Test: compiles

This reverts commit 119f521b1b03ce29c2e7f79c132483313e30a80a.

Change-Id: I16ff36c3c0c919056808e734dfbfc8cd9c8ca1d1
diff --git a/generateCppImpl.cpp b/generateCppImpl.cpp
index 25310f5..caa0ac0 100644
--- a/generateCppImpl.cpp
+++ b/generateCppImpl.cpp
@@ -104,7 +104,7 @@
 
     Formatter out(file);
 
-    const std::string guard = makeHeaderGuard(baseName);
+    const std::string guard = makeHeaderGuard(baseName, false /* indicateGenerated */);
 
     out << "#ifndef " << guard << "\n";
     out << "#define " << guard << "\n\n";