message: Disable PCH reading/writing
diff: #include <clang/Driver/Driver.h>
  #include <clang/Driver/Tool.h>
  #include <clang/Lex/Lexer.h>
  +#include <clang/Lex/PreprocessorOptions.h>
  #include <llvm/Support/Host.h>
  #include <llvm/Support/Path.h>
  @@ -148,6 +149,11 @@ buildCompilerInvocation(const std::string &main, std::vector<const char *> args,
  auto &isec = ci->getFrontendOpts().Inputs;
  if (isec.size())
  isec[0] = FrontendInputFile(main, isec[0].getKind(), isec[0].isSystem());
  + // clangSerialization has an unstable format. Disable PCH reading/writing
  + // to work around PCH mismatch problems.
  + ci->getPreprocessorOpts().ImplicitPCHInclude.clear();
  + ci->getPreprocessorOpts().PrecompiledPreambleBytes = {0, false};
  + ci->getPreprocessorOpts().PCHThroughHeader.clear();
  return ci;
  }
  