Add more flexibility to abi checking.

1) Marking a field "required" robs us of flexibility. Make fields optional
allows us to update the message format without needing to necessarily
update the reference abi-dumps.

2) Allow local warnings with the invocation of header-abi-diff.

Test: Added a function to libjpeg, got a warning claiming abi extended.

3) Introduce a flag which allows us to not filter any abi. This is
useful for cases when libraries do not include what they export. eg :
libsqlite.

Test: abi-dump size of libsqlite:
	without no-filter : 0
	with no-filter : ~9M

Change-Id: I6cfeacc8711f6df7a4136c2a27b5638988a2c54b

vndk/tools/header-checker/header-abi-diff/src/header_abi_diff.cpp

@@ -49,6 +49,10 @@ static llvm::cl::opt<bool> advice_only(
     "advice-only", llvm::cl::desc("Advisory mode only"), llvm::cl::Optional,
     llvm::cl::cat(header_checker_category));
 
+static llvm::cl::opt<bool> suppress_local_warnings(
+    "suppress_local_warnings", llvm::cl::desc("suppress local warnings"),
+    llvm::cl::Optional, llvm::cl::cat(header_checker_category));
+
 static llvm::cl::opt<bool> allow_extensions(
     "allow-extensions",
     llvm::cl::desc("Do not return a non zero status on extensions"),
@@ -80,6 +84,28 @@ int main(int argc, const char **argv) {
 
   CompatibilityStatus status  = judge.GenerateCompatibilityReport();
 
+  std::string status_str = "";
+  switch (status) {
+    case CompatibilityStatus::INCOMPATIBLE:
+      status_str = "broken";
+      break;
+    case CompatibilityStatus::EXTENSION:
+      status_str = "extended";
+      break;
+    default:
+      break;
+  }
+
+  if (!suppress_local_warnings && status) {
+    llvm::errs() << "******************************************************\n"
+                 << "VNDK Abi "
+                 << status_str
+                 << ":"
+                 << " Please check compatiblity report at : "
+                 << compatibility_report << "\n"
+                 << "*****************************************************\n";
+  }
+
   if (advice_only) {
     return CompatibilityStatus::COMPATIBLE;
   }