[boring] Also exclude _-prefixed typealiases in tool/ffigen.dart

pkgs/boring/lib/src/bindings/boringssl.g.dart

diff --git a/pkgs/boring/lib/src/bindings/boringssl.g.dart b/pkgs/boring/lib/src/bindings/boringssl.g.dart
index 301f1d3..e01405a 100644
--- a/pkgs/boring/lib/src/bindings/boringssl.g.dart
+++ b/pkgs/boring/lib/src/bindings/boringssl.g.dart
@@ -36427,17 +36427,6 @@
 
 final class _IO_FILE extends ffi.Opaque {}
 
-/// Deprecated private functions (hidden).
-///
-/// TODO(crbug.com/boringssl/499): Migrate callers to the typed wrappers, or at
-/// least the new names and remove the old ones.
-///
-/// TODO(b/290792019, b/290785937): Ideally these would at least be inline
-/// functions, so we do not squat the symbols.
-typedef _STACK = OPENSSL_STACK;
-typedef __time_t = ffi.Long;
-typedef Dart__time_t = int;
-
 /// aes_key_st should be an opaque type, but EVP requires that the size be
 /// known.
 final class aes_key_st extends ffi.Struct {
@@ -38577,7 +38566,7 @@
 
 final class stack_st_void extends ffi.Opaque {}
 
-typedef time_t = __time_t;
+typedef time_t = ffi.Long;
 
 final class tm extends ffi.Struct {
   @ffi.Int()

pkgs/boring/tool/ffigen.dart

diff --git a/pkgs/boring/tool/ffigen.dart b/pkgs/boring/tool/ffigen.dart
index 403df13..86e6509 100644
--- a/pkgs/boring/tool/ffigen.dart
+++ b/pkgs/boring/tool/ffigen.dart
@@ -129,7 +129,9 @@
           node.isIncluded = node.originalName.startsWith('ERR_LIB_');
         },
         typealias: (node) {
-          node.isIncluded = TypealiasInclude.always;
+          node.isIncluded = !node.originalName.startsWith('_')
+              ? TypealiasInclude.always
+              : TypealiasInclude.never;
         },
         macroConstant: (node) {
           final name = node.originalName;